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Thursday, January 18, 2024

• Scientists, Farmers and Managers Work Together to Avoid the Decline of the Little Bustard, an Endangered Steppe Bird

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• Rain Can Spoil a Wolf Spider's Day, Too
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Thursday, January 11, 2024

• Oldest Known Fossilized Skin Is 21 Million Years Older Than Previous Examples
• Need for Speed: How Hummingbirds Switch Mental Gears in Flight

Wednesday, January 10, 2024

• A Red Knot's Character Is Formed in First Year of Life

Tuesday, January 9, 2024

• Rallying for a Better Badminton Birdie

Monday, January 8, 2024

• Widespread Population Collapse of African Raptors
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• Feathers from Deceased Birds Help Scientists Understand New Threat to Avian Populations

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• How Technology and Economics Can Help Save Endangered Species

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• Daily Singing Workout Keeps Songbird Males Attractive
• The Configuration of Green Spaces in Cities Determines the Characteristics of Their Birds

Monday, December 11, 2023

• Extremely Rare Bird Captured on Film
• Millions of Birds Lose Precious Energy Due to Fireworks on New Year's Eve

Friday, December 8, 2023

• Suburban Backyard Home to More Than 1,000 Species

Thursday, December 7, 2023

• Wild Birds Lead People to Honey -- And Learn from Them

Wednesday, December 6, 2023

• Feathered Friends Can Become Unlikely Helpers for Tropical Coral Reefs Facing Climate Change Threat
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Monday, December 4, 2023

• Artificial Light Is Luring Birds to Cities and Sometimes to Their Deaths

Wednesday, November 29, 2023

• Identifying Australia's Most Elusive Birds
• Unknown Animals Were Leaving Bird-Like Footprints in Late Triassic Southern Africa

Friday, November 17, 2023

• Like the Phoenix, Australia's Giant Birds of Prey Rise Again from Limestone Caves

Thursday, November 16, 2023

• Temperature Variability Reduces Nesting Success
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• Forget Social Distancing: House Finches Become More Social When Sick

Wednesday, November 15, 2023

• Surveilling Wetlands for Infectious Bird Flu -- And Finding It
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• Geese 'keep Calm and Carry On' After Deaths in the Flock

Thursday, November 9, 2023

• Hummingbirds' Unique Sideways Flutter Gets Them Through Small Apertures
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Thursday, October 26, 2023

• Roosters Might Recognize Themselves in the Mirror

Wednesday, October 25, 2023

• Rider on the Storm: Shearwater Seabird Catches an 11 Hour Ride Over 1,000 Miles in a Typhoon

Tuesday, October 24, 2023

• Finding the Genes That Help Kingfishers Dive Without Hurting Their Brains

Thursday, October 19, 2023

• Unearthing the Ecological Impacts of Cicada Emergences on North American Forests
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Tuesday, October 17, 2023

• Mimicking a Bird's Sticky Spit to Create Cellulose Gels
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• New Threat to Antarctic Fur Seals

Tuesday, October 10, 2023

• Death Is Only the Beginning: Birds Disperse Eaten Insects' Eggs

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• To Prepare for Next Pandemic, Researchers Tackle Bird Flu
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• Boo to a Goose -- New Animal Behaviour Tech Aims to Save Wildlife

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• New Insect Genus Discovered in One of the Most Biodiverse Rain Forest Regions in the World

Monday, September 25, 2023

• Caribbean Parrots Thought to Be Endemic Are Actually Relicts of Millennial-Scale Extinction
• Study Shows Birds That Have Evolved Greater Complexity Are Less Biodiverse

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• Migratory Birds Can Be Taught to Adjust to Climate Change

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• Researchers' Analysis of Perching Birds Points to New Answers in Evolutionary Diversification
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• Urban Light Pollution Linked to Smaller Eyes in Birds
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• Clever Lapwings Use Cover to Hide in Plain Sight
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• Protected Nature Reserves Alone Are Insufficient for Reversing Biodiversity Loss

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• Published: 01 April 2024

Complexity of avian evolution revealed by family-level genomes

• Josefin Stiller   ORCID: orcid.org/0000-0001-6009-9581 1 ,
• Shaohong Feng   ORCID: orcid.org/0000-0002-2462-7348 2 , 3 , 4 , 5 ,
• Al-Aabid Chowdhury 6 ,
• Iker Rivas-González   ORCID: orcid.org/0000-0002-0515-0628 7 ,
• David A. Duchêne   ORCID: orcid.org/0000-0002-5479-1974 8 ,
• Qi Fang   ORCID: orcid.org/0000-0002-9181-8689 9 ,
• Yuan Deng 9 ,
• Alexey Kozlov   ORCID: orcid.org/0000-0001-7394-2718 10 ,
• Alexandros Stamatakis   ORCID: orcid.org/0000-0003-0353-0691 10 , 11 , 12 ,
• Santiago Claramunt   ORCID: orcid.org/0000-0002-8926-5974 13 , 14 ,
• Jacqueline M. T. Nguyen   ORCID: orcid.org/0000-0002-3076-0006 15 , 16 ,
• Simon Y. W. Ho   ORCID: orcid.org/0000-0002-0361-2307 6 ,
• Brant C. Faircloth   ORCID: orcid.org/0000-0002-1943-0217 17 ,
• Julia Haag   ORCID: orcid.org/0000-0002-7493-3917 10 ,
• Peter Houde   ORCID: orcid.org/0000-0003-4541-5974 18 ,
• Joel Cracraft   ORCID: orcid.org/0000-0001-7587-8342 19 ,
• Metin Balaban 20 ,
• Uyen Mai 21 ,
• Guangji Chen   ORCID: orcid.org/0000-0002-9441-1155 9 , 22 ,
• Rongsheng Gao 9 , 22 ,
• Chengran Zhou   ORCID: orcid.org/0000-0002-9468-5973 9 ,
• Yulong Xie 2 ,
• Zijian Huang 2 ,
• Zhen Cao 23 ,
• Zhi Yan   ORCID: orcid.org/0000-0003-2433-5553 23 ,
• Huw A. Ogilvie   ORCID: orcid.org/0000-0003-1589-6885 23 ,
• Luay Nakhleh   ORCID: orcid.org/0000-0003-3288-6769 23 ,
• Bent Lindow   ORCID: orcid.org/0000-0002-1864-4221 24 ,
• Benoit Morel 10 , 11 ,
• Jon Fjeldså   ORCID: orcid.org/0000-0003-0790-3600 24 ,
• Peter A. Hosner   ORCID: orcid.org/0000-0001-7499-6224 24 , 25 ,
• Rute R. da Fonseca   ORCID: orcid.org/0000-0002-2805-4698 25 ,
• Bent Petersen   ORCID: orcid.org/0000-0002-2472-8317 8 , 26 ,
• Joseph A. Tobias   ORCID: orcid.org/0000-0003-2429-6179 27 ,
• Tamás Székely   ORCID: orcid.org/0000-0003-2093-0056 28 , 29 ,
• Jonathan David Kennedy 30 ,
• Andrew Hart Reeve   ORCID: orcid.org/0000-0001-5233-6030 24 ,
• Andras Liker 31 , 32 ,
• Martin Stervander   ORCID: orcid.org/0000-0002-6139-7828 33 ,
• Agostinho Antunes   ORCID: orcid.org/0000-0002-1328-1732 34 , 35 ,
• Dieter Thomas Tietze   ORCID: orcid.org/0000-0001-6868-227X 36 ,
• Mads Bertelsen 37 ,
• Fumin Lei   ORCID: orcid.org/0000-0001-9920-8167 38 , 39 ,
• Carsten Rahbek   ORCID: orcid.org/0000-0003-4585-0300 25 , 30 , 40 , 41 ,
• Gary R. Graves   ORCID: orcid.org/0000-0003-1406-5246 30 , 42 ,
• Mikkel H. Schierup   ORCID: orcid.org/0000-0002-5028-1790 7 ,
• Tandy Warnow 43 ,
• Edward L. Braun   ORCID: orcid.org/0000-0003-1643-5212 44 ,
• M. Thomas P. Gilbert   ORCID: orcid.org/0000-0002-5805-7195 8 , 45 ,
• Erich D. Jarvis 46 , 47 ,
• Siavash Mirarab   ORCID: orcid.org/0000-0001-5410-1518 48 &
• Guojie Zhang   ORCID: orcid.org/0000-0001-6860-1521 2 , 3 , 5 , 49  

Nature ( 2024 ) Cite this article

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We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.

• Evolutionary biology
• Genome evolution
• Molecular evolution
• Phylogenetics

Despite tremendous efforts in the past decades, relationships among main avian lineages remain heavily debated without a clear resolution. Discrepancies have been attributed to diversity of species sampled, phylogenetic method, and the choice of genomic regions 1–3 . Here, we address these issues by analyzing genomes of 363 bird species 4 (218 taxonomic families, 92% of total). Using intergenic regions and coalescent methods, we present a well-supported tree but also a remarkable degree of discordance. The tree confirms that Neoaves experienced rapid radiation at or near the Cretaceous–Paleogene (K–Pg) boundary. Sufficient loci rather than extensive taxon sampling were more effective in resolving difficult nodes. Remaining recalcitrant nodes involve species that challenge modeling due to extreme GC content, variable substitution rates, incomplete lineage sorting, or complex evolutionary events such as ancient hybridization. Assessment of the impacts of different genomic partitions showed high heterogeneity across the genome. We discovered sharp increases in effective population size, substitution rates, and relative brain size following the K–Pg extinction event, supporting the hypothesis that emerging ecological opportunities catalyzed the diversification of modern birds. The resulting phylogenetic estimate offers novel insights into the rapid radiation of modern birds and provides a taxon-rich backbone tree for future comparative studies.

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Author information, authors and affiliations.

Section for Ecology and Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark

Josefin Stiller

Center for Evolutionary & Organismal Biology, & Women’s Hospital, Zhejiang University School of Medicine, Hangzhou, China

Shaohong Feng, Yulong Xie, Zijian Huang & Guojie Zhang

Liangzhu Laboratory, Zhejiang University Medical Center, Hangzhou, China

Shaohong Feng & Guojie Zhang

Department of General Surgery, Sir Run-Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China

• Shaohong Feng

Innovation Center of Yangtze River Delta, Zhejiang University, Jiashan, China

School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia

Al-Aabid Chowdhury & Simon Y. W. Ho

Bioinformatics Research Centre, Aarhus University, Aarhus, Denmark

Iker Rivas-González & Mikkel H. Schierup

Center for Evolutionary Hologenomics, The Globe Institute, University of Copenhagen, Copenhagen, Denmark

David A. Duchêne, Bent Petersen & M. Thomas P. Gilbert

BGI-Shenzhen, Beishan Industrial Zone, Shenzhen, China

Qi Fang, Yuan Deng, Guangji Chen, Rongsheng Gao & Chengran Zhou

Computational Molecular Evolution Group, Heidelberg Institute for Theoretical Studies, Heidelberg, Germany

Alexey Kozlov, Alexandros Stamatakis, Julia Haag & Benoit Morel

Institute of Computer Science, Foundation for Research and Technology Hellas, Heraklion, Greece

Alexandros Stamatakis & Benoit Morel

Institute for Theoretical Informatics, Karlsruhe Institute of Technology, Karlsruhe, Germany

Alexandros Stamatakis

Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada

Santiago Claramunt

Department of Natural History, Royal Ontario Museum, Toronto, Ontario, Canada

College of Science and Engineering, Flinders University, Bedford Park, South Australia, Australia

Jacqueline M. T. Nguyen

Research Institute, Australian Museum, Sydney, New South Wales, Australia

Department of Biological Sciences and Museum of Natural Science, Louisiana State University, Baton Rouge, LA, USA

Brant C. Faircloth

Department of Biology, New Mexico State University, Las Cruces, NM, USA

Peter Houde

Department of Ornithology, American Museum of Natural History, New York, NY, USA

Joel Cracraft

Bioinformatics and Systems Biology Graduate Program, University of California San Diego, La Jolla, CA, USA

Metin Balaban

Computer Science and Engineering, University of California San Diego, La Jolla, CA, USA

College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China

Guangji Chen & Rongsheng Gao

Department of Computer Science, Rice University, Houston, TX, USA

Zhen Cao, Zhi Yan, Huw A. Ogilvie & Luay Nakhleh

Natural History Museum Denmark, University of Copenhagen, Copenhagen, Denmark

Bent Lindow, Jon Fjeldså, Peter A. Hosner & Andrew Hart Reeve

Center for Global Mountain Biodiversity, Globe Institute, University of Copenhagen, Copenhagen, Denmark

Peter A. Hosner, Rute R. da Fonseca & Carsten Rahbek

Centre of Excellence for Omics-Driven Computational Biodiscovery (COMBio), Faculty of Applied Sciences, AIMST University, Bedong, Kedah, Malaysia

Bent Petersen

Department of Life Sciences, Imperial College London, Silwood Park, Ascot, UK

Joseph A. Tobias

Milner Centre for Evolution, University of Bath, Bath, UK

Tamás Székely

ELKH-DE Reproductive Strategies Research Group, University of Debrecen, Debrecen, Hungary

Center for Macroecology, Evolution, and Climate, The Globe Institute, University of Copenhagen, Copenhagen, Denmark

Jonathan David Kennedy, Carsten Rahbek & Gary R. Graves

HUN-REN-PE Evolutionary Ecology Research Group, University of Pannonia, Veszprém, Hungary

Andras Liker

Behavioural Ecology Research Group, Center for Natural Sciences, University of Pannonia, Veszprém, Hungary

Bird Group, Natural History Museum, Akeman St, Tring, Hertfordshire, United Kingdom

Martin Stervander

CIIMAR/CIMAR, Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Porto, Portugal

Agostinho Antunes

Department of Biology, Faculty of Sciences, University of Porto, Porto, Portugal

NABU, Berlin, Germany

Dieter Thomas Tietze

Centre for Zoo and Wild Animal Health, Copenhagen Zoo, Frederiksberg, Denmark

Mads Bertelsen

Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China

College of Life Science, University of Chinese Academy of Sciences, Beijing, China

Institute of Ecology, Peking University, Beijing, China

Carsten Rahbek

Danish Institute for Advanced Study, University of Southern Denmark, Odense, Denmark

Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA

Gary R. Graves

University of Illinois Urbana-Champaign, Champaign, IL, USA

Tandy Warnow

Department of Biology, University of Florida, Gainesville, FL, USA

Edward L. Braun

University Museum, NTNU, Trondheim, Norway

M. Thomas P. Gilbert

Vertebrate Genome Lab, The Rockefeller University, New York, NY, USA

Erich D. Jarvis

Howard Hughes Medical Institute, Durham, NC, USA

University of California, San Diego, San Diego, CA, USA

Siavash Mirarab

Villum Center for Biodiversity Genomics, Department of Biology, University of Copenhagen, Copenhagen, Denmark

Guojie Zhang

You can also search for this author in PubMed   Google Scholar

Corresponding authors

Correspondence to Josefin Stiller , Siavash Mirarab or Guojie Zhang .

Supplementary information

Supplementary information.

This file contains Supplementary Methods and Supplementary Results.

Reporting Summary

Peer review file, supplementary data.

Table of all sequenced species with taxonomic grouping according to Howard & Moore. 4th Edition and accession numbers of the used genome assemblies. Given as a separate tab-delimited text file.

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Cite this article.

Stiller, J., Feng, S., Chowdhury, AA. et al. Complexity of avian evolution revealed by family-level genomes. Nature (2024). https://doi.org/10.1038/s41586-024-07323-1

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Received : 25 April 2023

Accepted : 15 March 2024

Published : 01 April 2024

DOI : https://doi.org/10.1038/s41586-024-07323-1

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• Open access
• Published: 02 November 2021

Birds and plastic pollution: recent advances

• Limin Wang 1 ,
• Ghulam Nabi 1 ,
• Liyun Yin 1 ,
• Yanqin Wang 1 ,
• Shuxin Li 1 ,
• Zhuang Hao 1 &
• Dongming Li 1  

Avian Research volume  12 , Article number:  59 ( 2021 ) Cite this article

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Plastic waste and debris have caused substantial environmental pollution globally in the past decades, and they have been accumulated in hundreds of terrestrial and aquatic avian species. Birds are susceptible and vulnerable to external environments; therefore, they could be used to estimate the negative effects of environmental pollution. In this review, we summarize the effects of macroplastics, microplastics, and plastic-derived additives and plastic-absorbed chemicals on birds. First, macroplastics and microplastics accumulate in different tissues of various aquatic and terrestrial birds, suggesting that birds could suffer from the macroplastics and microplastics-associated contaminants in the aquatic and terrestrial environments. Second, the detrimental effects of macroplastics and microplastics, and their derived additives and absorbed chemicals on the individual survival, growth and development, reproductive output, and physiology, are summarized in different birds, as well as the known toxicological mechanisms of plastics in laboratory model mammals. Finally, we identify that human commensal birds, long-life-span birds, and model bird species could be utilized to different research objectives to evaluate plastic pollution burden and toxicological effects of chronic plastic exposure.

Along with global industrialization and modernization, the production and consumption of plastic items have increased substantially since the early 1950s (Geyer et al. 2017 ; MacLeod et al. 2021 ). Approximately, 8.3 billion metric tons of virgin plastic were produced up to 2017, and 12 billion tons of plastic wastes are expected to be found in the natural environment by 2050 (Geyer et al. 2017 ). Most plastic products (macroplastics, diameter > 5 mm) are not biodegradable and break down into small plastic particles that can be easily spread to various environments by the action of wind and waves owing to their small size, lightweight, high durability, and extended stability (Susanti et al. 2020 ). In recent years, plastic particles with diameter ≤ 5 mm (microplastics, MPs) and ≤ 1 μm (nanoplastics, NPs) have been increasingly observed in various compositions, shapes, morphologies, and textures in atmospheric, terrestrial, and marine environments, and they can enter the food chain either by inhalation or by ingestion (Susanti et al. 2020 ; Fig.  1 ). MPs have also been discovered in remote areas such as polar regions (Bessa et al. 2019 ), Mount Everest (Napper et al. 2020 ), and the Mariana Trench (Jamieson et al. 2019 ). MPs can act as vectors for pathogens and chemical pollutants because of their environmental persistence and potential ecotoxicity, which pose significant health and ecological concerns (Amelineau et al. 2016 ; Nabi et al. 2019 ). Furthermore, they are bioavailable for ingestion by a variety of wild organisms (Cole et al. 2013 ; Bessa et al. 2018 ; Nelms et al. 2019 ) and can enter food chains through trophic transfer, causing severe threats to biodiversity and ecosystems (Karami et al. 2016 ; Dawson et al. 2018 ; Zhu et al. 2018 ). Therefore, the accumulation of plastic waste and debris in the environment has continuously increased, resulting in substantial environmental pollution (Rochman et al. 2013 ; Wilcox et al. 2015 ; Zhu et al. 2019 ).

The cycling process of macroplastics and microplastics in different ecosystems (red arrow) and potential uptake ways by birds from different ecological groups (orange arrow)

Birds have the largest number of species (more than 10,000 living species) among the tetrapod classes (Ducatez and Lefebvre 2014 ). They are endotherms organisms that are widely distributed in various habitats worldwide, from the equator to polar areas, and from oceans and freshwater to high plateaus, and they exhibit flight-related morphological and physiological traits that enable them to occupy different habitats and become important members of many ecosystems (Orme et al. 2006 ) (Fig.  1 ). Compared with non-flying animals, birds have a higher metabolic rate (McNab 2009 ), better antioxidant capacity (Costantini 2008 ), prolonged lifespan (Munshi-South and Wilkinson 2010 ) and short but efficient digestive tract (Caviedes-Vidal et al. 2007 ). They are believed to be highly sensitive and vulnerable to external conditions, and therefore, could be used to monitor environmental changes and assess the negative effects of environmental pollution (Carral-Murrieta et al. 2020 ; Li et al. 2021 ; Nabi et al. 2021 ). Given that birds in particular mistake plastic for prey, macroplastics or MPs have been found in the gastrointestinal tracts, feces, and even in feathers and other tissues or organs of several hundred avian species from freshwater, terrestrial, and marine ecosystems (Carey 2011 ; Gall and Thompson 2015 ; Wilcox et al. 2015 ; Zhao et al. 2016 ). Here, we review the occurrence of plastics and MPs in aquatic and terrestrial birds (Fig.  1 ); summarize the effects of plastics, MPs, plastics-derived additives, and plastic-absorbed chemicals; and suggest directions for further research in the field of plastic pollution in birds.

Macroplastics and microplastics in aquatic and terrestrial birds

Plastic debris is ubiquitous in oceans, and its potential impacts on a wide range of marine organisms have raised serious concerns (Andrady 2011 ; Jambeck et al. 2015 ; Yin et al. 2018 , 2019 ). Globally, the proportion of MPs to the total weight of plastic accumulated in the environment by 2060 is estimated at 13.2% (Andrady 2011 ). Macroplastics and MPs in the oceans are similar in size and appearance to tiny marine organisms (e.g., zooplankton), and they can be wrongly regarded as prey by marine animals such as fish and shellfish (Waring et al. 2018 ). These marine animals are the primary food resource of many seabirds, so that the seabirds are particularly susceptible to plastic exposure because of their high rates of ingestion of contaminated prey (Barbieri et al. 2010 ). It is estimated that up to 78% of identified species of seabirds have deposited MPs in their digestive tracts since the 1960s (Wilcox et al. 2015 ; Basto et al. 2019 ), and more than 99% of over 300 seabird species are expected to have ingested plastic debris by 2050 (Wilcox et al. 2015 ). The positive correlation between MPs in feathers and fecal samples in geese and ducks (Reynolds and Ryan 2018 ) suggests that MPs can accumulate in different tissues of their bodies. Seabirds spread particulate plastics at colonies through regurgitation (Lindborg et al. 2012 ; Hammer et al. 2016 ) and guano deposition, thereby increasing the concentration of chemical contaminants near their colonies (Blais et al. 2005 ). Therefore, seabirds function as vectors for marine-derived MPs and plastic-associated contaminants in the aquatic and terrestrial environments.

Terrestrial birds are an essential component of land ecosystems, with various ecological functions in the food web (Carlin et al. 2020 ). Zhao et al. ( 2016 ) reported that MPs were discovered in the gastrointestinal tracts of 16 out of 17 terrestrial bird species. Unlike many studies on aquatic birds, there are few studies on terrestrial birds, except for plastic ingestion by several top bird predators (Carlin et al. 2020 ; Ballejo et al. 2021 ). The occurrence of macroplastics and MPs has been reported in some raptors, because raptors are top predators, and has relatively large foraging areas, and a longer lifespan (Houston et al. 2007 ; Carlin et al. 2020 ; Ballejo et al. 2021 ). For instance, the California Condor ( Gymnogyps californianus ), a critically endangered species, has been reported to ingest plastic from rubbish dumps (Houston et al. 2007 ), which is considered one of the most important causes of death in nestlings (Rideout et al. 2012 ). In addition, another study showed that MPs were significantly more abundant in the digestive tract tissue of Red-shouldered Hawk ( Buteo lineatus ), that consumes small mammals, snakes, and amphibians, than in fish feeding Osprey ( Pandion haliaetus ) (Carlin et al. 2020 ). Vultures are obligate scavengers, and many of them use rubbish dumps as food resources worldwide, including the Andean Condor ( Vultur gryphus ), Black Vulture ( Coragyps atratus ), and Turkey Vulture ( Cathartes aura ) (Houston et al. 2007 ; Plaza et al. 2018 ; Carlin et al. 2020 ; Ballejo et al. 2021 ). This feeding habit increases their exposure risks to MPs consumption through organic waste and synthetic materials, which can cause intestinal obstructions, nutritional problems, infections, and metabolic alterations (Plaza et al. 2018 ; Tauler-Ametlller et al. 2019 ). Although small-sized terrestrial birds (e.g., passerines) are highly diversified and widely distributed relative to raptors (Yu et al. 2014 ), little is known about the relationship between the occurrence of macroplastics and MPs in small-sized terrestrial birds.

Effects of macroplastics and microplastics on birds

Various negative consequences are resulting from interactions between wildlife and plastic debris. The most obvious and immediate consequences include entanglement (Derraik 2002 ; Ryan 2018 ; Lavers et al. 2020 ), nutritional deprivation (Lavers et al. 2014 ), and damage or obstruction of the gut (Pierce et al. 2004 ). Particularly, more and more birds are severely affected by entanglement owing to the increasing presence of plastic litter (Gregory 2009 ; Roman et al. 2019 ), e.g., the large number of face masks carelessly discarded during the COVID-19 pandemic (Patrício Silva et al. 2021 ). Entanglement can lead to injuries, drowning, and even suffocation, which can reduce predation efficiency and increase the probability of being preyed upon (Derraik 2002 ; Gall and Thompson 2015 ). Furthermore, large plastic fragments and tiny plastic particles are also frequently ingested by birds (Derraik 2002 ; Ryan 2018 ; Lavers et al. 2020 ). For example, microplastic fibers, beads, and macroplastics have been found embedded in the intestinal wall of Red-shouldered Hawk and Osprey, which suggests that these materials can remain in the intestines longer than other indigestible items that pass through (Carlin et al. 2020 ). Several pioneering studies have reported that the deposited and aggregated MPs or larger plastic debris can cause bleeding, blockage of the digestive tract, ulcers, or perforations of the gut, which can produce a deceptive feeling of satiation (Derraik 2002 ; Pierce et al. 2004 ), lead to starvation (Derraik 2002 ; Pierce et al. 2004 ), or cause direct mortality (Derraik 2002 ; Roman et al. 2019 ). For example, the volume of plastic ingested (plastic burden) by the Northern Gannet ( Morus bassanus ) and the Great Shearwater ( Puffinus gravis ) can be associated with damage or obstruction of the gut, reduced body weight, slower growth rate, and increased mortality (Pierce et al. 2004 ). Similarly, a decreased growth rate induced by plastic ingestion was observed in the chicks of Flesh-footed Shearwater ( Puffinus carneipes ) (Lavers et al. 2014 ) and Japanese Quail ( Coturnix japonica ) (Roman et al. 2019 ), which likely resulted from reduced stomach capacity rather than toxicological effects (Fig. 2 ).

The physical impairment and toxicological effects of environmental plastic pollution on birds

Some studies have found that ingestion of MPs has reproductive toxicity to birds (Fossi et al. 2018 ; Roman et al. 2019 ). For example, chicks of Japanese Quail with observed plastic ingestion exhibited a minor delay in sexual maturity, and a higher incidence of epididymal intra-epithelial cysts in males, although there were no effects on reproductive success (Roman et al. 2019 ). Similarly, the ingestion of MPs can also reduce the reproductive output of Flesh-footed Shearwater (Fossi et al. 2018 ). Carey ( 2011 ) observed that the plastics or microplastics ingested by adult Short-tailed Shearwater ( Ardenna tenuirostris ) could be passed to their chicks. Furthermore, ingestion of MPs by birds can activate inflammatory responses, and lead to reducing food intake, delayed ovulation, and increased mortality (Wright et al. 2013 ; Carbery et al. 2018 ; Fossi et al. 2018 ) (Fig. 2 ). In this context, it is important to determine the potential MPs concentration that is detrimental or sublethal to body condition, development, growth, reproduction, and other physiological functions in birds (Puskic et al. 2019 ).

Effects of plastics-derived additives and plastics-adsorbed chemicals on birds

Plastic debris contains a wide range of additives and toxic chemicals sorbed from the environment (Hirai et al. 2011 ), which can have various adverse effects on wildlife organisms (Chen et al. 2019 ; Tanaka et al. 2020 ). The European Chemicals Agency has listed approximately 400 plastic additives, including organotins, triclosan, phthalates, brominated flame retardants, bisphenols, and diethyl hexyl phthalate (DEHP) (Du et al. 2017 ; Hermabessiere et al. 2017 ; Zhang et al. 2018 ). The accumulation of plastic additives has been reported in several seabirds, including the Streaked Shearwater ( Calonectris leucomelas ) (Teuten et al. 2009 ), Short-tailed Shearwaters (Yamashita et al. 2011 ), and Flesh-footed Shearwaters (Lavers et al. 2014 ), suggesting that plastics are a direct carrier of chemicals to seabirds. Among these chemicals, many studies confirm that DEHP can cause weight gain in European Starling ( Sturnus vulgaris ) (O’Shea and Stafford, 1980 ) and is potentially toxic to the kidneys (Li et al. 2018 ), liver (Zhang et al. 2018 ), and cerebellum (Du et al. 2017 ) in Japanese Quail.

In addition, owing to their hydrophobic nature and relatively large surface area, MPs can adsorb numerous environmental contaminants, such as POPs, heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), antibiotics, and endocrine-disrupting compounds (EDCs) (Rathi et al. 2019 ; Reddy et al. 2019 ). Previous studies have shown that ingestion of toxic substances adsorbed on MPs can induce malnutrition, endocrine disruption, and issues in the reproductive biology of Japanese Quail (Roman et al. 2019 ) and several species of seabirds, including Kelp Gull ( Larus dominicanus ) (Barbieri 2010 ), Short-tailed Shearwater (Tanaka et al. 2013 ), White-chinned Petrel ( Procellaria aequinoctialis ), Slender-billed Prion ( Pachyptila belcheri ), Great Shearwater, Black-browed Albatross ( Thalassarche melanophrys ), and Southern Giant Petrel ( Macronectes giganteus ) (Susanti et al. 2020 ). Chronic exposure to EDCs can have several negative effects on the developmental and reproductive biology of Japanese Quail (Ottinger et al. 2008 ), Tree Swallow ( Tachycineta bicolor ) (McCarty and Second 2000 ), American Kestrel ( Falco sparverius ) (Fisher et al. 2001 ), Great Blue Heron ( Ardea herodias ) (Sanderson et al. 1994 ) and White Ibis ( Eudocimus albus ) (Jayasena et al. 2011 ), and it also can impair immune and thyroid functions in Japanese Quails (Ottinger et al. 2008 ). Furthermore, EDCs cause poor reproductive output because of embryonic death, chick deformities, eggshell thinning, and even death in Japanese Quails (Ottinger et al. 2005 ). Previous studies have shown that traditional pollutants, such as heavy metals and organic pollutants (POPs) are detrimental to the health of birds. For example, heavy metals have adverse effects on the testicular function and sperm quality of Eurasian Tree Sparrows ( Passer montanus ) (Yang et al. 2020 ) and White Ibises (Frederick and Jayasena 2011 ), and POPs exert numerous negative effects on endocrine, immune and neural system in White-tailed Eagle ( Haliaeetus albicilla ) (Sletten et al. 2016 ) and reproduction, and development, and growth in other bird species (Hao et al. 2021 ). However, it is quite challenging to find pertinent data for each toxicant because of the large number of plastic-associated toxicants identified in wild avian species.

Known toxicological and physiological effects of macroplastics and microplastics in other animals

Plastic debris and MPs have also been found in the digestive tracts of a variety of animal groups from various environments. First, plastics can cause entanglement or lead to starvation or intestinal blockages upon ingestion (Gregory 2009 ; Provencher et al. 2017 ). Second, MPs can be deposited in the mucus layer secreted by the cells of the gut wall, and then transported to other organs or tissues via circulation (Lu et al. 2018 ; Jin et al. 2019 ). In addition to the physical impairment and histological variations in the intestines, the perils of MP ingestion include growth impediment and disorders of metabolism and behavior (Lu et al. 2018 ; Jin et al. 2019 ). MPs also impair filter feeders (mussels and clams) and induce DNA damage, oxidative injury, and antioxidative responses (clams) (Cedervall et al. 2012 ; Ribeira et al. 2017 ). Furthermore, endocrine disruption and neurotransmission dysfunction of marine species caused by MPs have been reported, in addition to genotoxicity (Rochman et al. 2014 ; Avio et al. 2015 ). Polystyrene MPs can adversely affect granulocytes and ovarian function in female rats through distinct signaling pathways (Hou et al. 2021 ).

Compared with plastic debris and MPs, NPs have a higher potential to negatively affect organisms because they can penetrate and accumulate in organs or tissues through systemic circulation (Kashiwada 2006 ; von Moos et al. 2012 ) and even pass biological barriers (Mattsson et al. 2016 ; Borisova 2018 ). NPs can interact with proteins, lipids, and carbohydrates, which affect transmembrane transport (Revel et al. 2018 ) and metabolism (Cedervall et al. 2012 ; Mattsson et al. 2015 ), and can lead to reproductive dysfunction and behavioral abnormalities in aquatic (Chae and An 2017 ; Mattsson et al. 2017 ; Prüst et al. 2020 ) and terrestrial (Amereh et al. 2020 ; Prüst et al. 2020 ) animals. Furthermore, NPs have induced adverse effects on the reproductive functions of laboratory mammals (Amereh et al. 2020 ; An et al. 2021 ; Jin et al. 2021 ), such as alterations in sperm morphology and viability, and lower serum testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) in mice and rats (Amereh et al. 2020 ). Polystyrene NPs can cause depression and behavioral and cognitive disorders in mice (da Costa Araújo and Malafaia 2021 ; Estrela et al. 2021 ). Despite the limited information on the toxicological effects of NPs on non-laboratory model animals, the above-mentioned effects of widely distributed NPs can be inferred to occur in free-living animals.

Future directions

The increasing demand for plastic products coupled with inadequate waste management and policy contributes to the ongoing and rapidly expanding environmental pollution of plastics (Rochman et al. 2013 ; Borrelle et al. 2017 ). MPs are hazardous not only to birds but also to other animals, including humans. In recent years, an increasing number of studies have identified the occurrence of plastics and plastics-associated toxicants in various animals associated with a significant increase in plastic pollution. Although an increasing number of studies have focused on the phenomenon of plastic deposition and toxicological effects in birds, the mechanisms throughout which MPs enter tissues and their potential health risks have not been fully clarified. Although MPs do not exhibit apparent toxicity, they can absorb toxic chemicals, which further challenges our understanding of the overall impacts of MPs. Further investigations are needed to determine whether the endocrine and toxicological effects of MPs-related contamination (e.g., plastics-derived additives and plastics-adsorbed chemicals) occur in wild birds with sufficient severity to be detrimental to fitness, and whether birds suffer ongoing disadvantages upon chronic low-level toxicity.

As birds have a great number of specific groups, different groups can be used to assess the plastic pollution burden, long-term effects of MPs exposure in various environments, and toxicological effects in the laboratory. For instance, human commensal species, such as the Eurasian Tree Sparrow (Sun et al. 2016 ; Li et al. 2019 ; Yang et al.  2019 ; Ding et al. 2021 ), House Sparrow ( P. domesticus ) (Hanson et al. 2020 ) and House Wren ( Troglodytes aedon ) (Juárez et al. 2020 ) utilize human resources in rural and urban areas and have a remarkably broad distribution range. These species could be used as bioindicators to evaluate the plastic pollution burden in different environments because they have been well studied in the past two decades. In addition, as long-lifespan species (e.g., albatrosses, shearwaters, and vultures) can breed over many decades (Moore 2008 ), they could be used to evaluate the potential toxicological effects of chronic plastic exposure on both individual survival and reproductive output (Kramar et al. 2019 ; Marín-Gómez et al. 2020 ; Sánchez et al. 2020 ). Furthermore, these species could be used to evaluate the effects of food contaminated with plastic debris and the intergenerational transfer of MPs through allofeeding of offsprings (Sánchez et al. 2020 ), as observed in the Cory’s Shearwater ( Calonectris diomedea ) fledglings (Rodríguez et al. 2012 ), Providence Petrel ( Pterodroma solandri ) (Bester et al. 2010 ), Black-footed Albatross ( Phoebastria nigripes ) (Rapp et al. 2017 ), Laysan Albatross ( P. immutabilis ) (Young et al. 2009 ), Short-tailed Shearwater (Carey 2011 ), Wedge-tailed Shearwater ( A. pacifica ) (Verlis et al. 2013 ), Flesh-footed Shearwater (Lavers et al. 2014 ), and other petrels (Rapp et al. 2017 ). Finally, model bird species (chicken and Japanese Quail) could be used to clarify the potential regulatory mechanisms associated with physiology, behavior, and neuroendocrinology upon exposure to different sizes of MPs.

NPs can cause more potent threats than MPs to mammals because they are small enough to accumulate in different tissues through systemic circulation (Estrela et al. 2021 ). In birds, one can predict that NPs might cause behavioral, physiological, and neuroendocrinological changes, although there has been no identified evidence, and further investigations are necessary. Furthermore, as birds build nests with many natural and human-related materials, the potential threat of plastic debris, MPs, or NPs as nest materials to embryonic and chick development needs to be further examined. Birds are unique and differ from other animal groups because of their behavior, physiology, and lifestyle. Further research should focus on the underlying toxicological mechanisms of MPs and NPs in the laboratory or free-living birds and the identification of consistent and inconsistent response mechanisms to plastics-related pollution (i.e., macroplastics, MPs, NPs, plastics-derived additives, and plastics-adsorbed chemicals) in birds and other animal groups.

Amelineau F, Bonnet D, Heitz O, Mortreux V, Harding AMA, Karnovsky N, et al. Microplastic pollution in the Greenland Sea: background levels and selective contamination of planktivorous diving seabirds. Environ Pollut. 2016;219:1131–9.

Article   CAS   PubMed   Google Scholar  

Amereh F, Babaei M, Eslami A, Fazelipour S, Rafiee M. The emerging risk of exposure to nano (micro) plastics on endocrine disturbance and reproductive toxicity: from a hypothetical scenario to a global public health challenge. Environ Pollut. 2020;261:114158.

An R, Wang XF, Yang L, Zhang JJ, Wang NN, Xu FB, et al. Polystyrene microplastics cause granulosa cells apoptosis and fibrosis in ovary through oxidative stress in rats. Toxicology. 2021;449:152665.

Andrady AL. Microplastics in the marine environment. Mar Pollut Bull. 2011;62:1596–605.

Avio CG, Gorbi S, Regoli F. Experimental development of a new protocol for extraction and characterization of microplastics in fish tissues: first observations in commercial species from Adriatic Sea. Mar Environ Res. 2015;111:18–26.

Ballejo F, Plaza P, Speziale KL, Lambertucci AP, Lambertucci SA. Plastic ingestion and dispersion by vultures may produce plastic islands in natural areas. Sci Total Environ. 2021;755: 142421.

Barbieri E, de Andrade PE, Filippini A, Souza dos Santos I, Borges Garcia CA. Assessment of trace metal concentration in feathers of seabird ( Larus dominicanus ) sampled in the Florianópolis, SC, Brazilian coast. Environ Monit Assess. 2010;169:631–8.

Basto MN, Nicastro KR, Tavares AI, McQuaid CD, Casero M, Azevedo F, et al. Plastic ingestion in aquatic birds in Portugal. Mar Pollut Bull. 2019;138:19–24.

Bessa F, Barría P, Neto JM, Frias JPGL, Otero V, Sobral P, et al. Occurrence of microplastics in commercial fish from a natural estuarine environment. Mar Pollut Bull. 2018;128:575–84.

Bessa F, Ratcliffe N, Otero V, Sobral P, Marques JC, Waluda CM, et al. Microplastics in gentoo penguins from the Antarctic region. Sci Rep. 2019;9:14191.

Article   PubMed   PubMed Central   CAS   Google Scholar  

Bester AJ, Priddel D, Klomp NI. Diet and foraging behaviour of the Providence petrel Pterodroma solandri . Mar Ornithol. 2010;39:163–72.

Google Scholar  

Blais JM, Kimpe LE, McMahon D, Keatley BE, Mallory ML, Douglas MSV, et al. Arctic seabirds transport marine-derived contaminants. Science. 2005;309:445.

Borisova T. Nervous system injury in response to contact with environmental, engineered and planetary micro- and nano-sized particles. Front Physiol. 2018;9:728.

Article   PubMed   PubMed Central   Google Scholar  

Borrelle SB, Rochman CM, Liboiron M, Bond AL, Lusher A, Bradshaw H, et al. Opinion: why we need an international agreement on marine plastic pollution. Proc Natl Acad Sci USA. 2017;114:9994–7.

Article   CAS   PubMed   PubMed Central   Google Scholar  

Carbery M, O’Connor W, Palanisami T. Trophic transfer of microplastics and mixed contaminants in the marine food web and implications for human health. Environ Int. 2018;115:400–9.

Article   PubMed   Google Scholar  

Carey MJ. Intergenerational transfer of plastic debris by short-tailed shearwaters ( Ardenna tenuirostris ). Emu. 2011;111:229–34.

Article   Google Scholar  

Carlin J, Craig C, Little S, Donnelly M, Fox D, Zhai L. Microplastic accumulation in the gastrointestinal tracts in birds of prey in central Florida, USA. Environ Pollut. 2020;264:114633.

Carral-Murrieta CO, García-Arroyo M, Marín-Gómez OH, Sosa-López JR, MacGregor-Fors I. Noisy environments: untangling the role of anthropogenic noise on bird species richness in a Neotropical city. Avian Res. 2020;11:32.

Caviedes-Vidal E, McWhorter TJ, Lavin SR, Chediack JG, Tracy CR, Karasov WH. The digestive adaptation of flying vertebrates: high intestinal paracellular absorption compensates for smaller guts. Proc Natl Acad Sci USA. 2007;104:19132–7.

Cedervall T, Hansson LA, Lard M, Frohm B, Linse S. Food chain transport of nanoparticles affects behaviour and fat metabolism in fish. PLoS ONE. 2012;7:e32254.

Chae Y, An YJ. Effects of micro- and nanoplastics in aquatic ecosystems: current research trends and perspectives. Mar Pollut Bull. 2017;124:624–32.

Chen Q, Allgeier A, Yin D, Hollert H. Leaching of endocrine disrupting chemicals from marine microplastics and mesoplastics under common life stress conditions. Environ Int. 2019;130:104938.

Cole M, Lindeque P, Fileman E, Halsband C, Goodhead R, Moger J, et al. Microplastic ingestion by zooplankton. Environ Sci Technol. 2013;47:6646–55.

Costantini D. Oxidative stress in ecology and evolution: lessons from avian studies. Ecol Lett. 2008;11:1238–51.

da Costa Araújo AP, Malafaia G. Microplastic ingestion induces behavioral disorders in mice: a preliminary study on the trophic transfer effects via tadpoles and fish. J Hazard Mater. 2021;401:123263.

Article   PubMed   CAS   Google Scholar  

Dawson A, Huston W, Kawaguchi S, King C, Cropp R, Wild S, et al. Bengtson nash, uptake and depuration kinetics influence microplastic bioaccumulation and toxicity in Antarctic Krill ( Euphausia superba ). Environ Sci Technol. 2018;52:3195–201.

Derraik JG. The pollution of the marine environment by plastic debris: a review. Mar Pollut Bull. 2002;44:842–52.

Ding B, Zhao Y, Sun Y, Zhang Q, Li M, Nabi G, et al. Coping with extremes: lowered myocardial phosphofructokinase activities and glucose content but increased fatty acids content in highland Eurasian Tree Sparrows. Avian Res. 2021;12:44.

Du ZH, Xia J, Sun XC, Li XN, Zhang C, Zhao HS, et al. A novel nuclear xenobiotic receptors (AhR/ PXR/CAR)-mediated mechanism of DEHP-induced cerebellar toxicity in quails ( Coturnix Japonica ) via disrupting CYP enzyme system homeostasis. Environ Pollut. 2017;226:435–43.

Ducatez S, Lefebvre L. Patterns of research effort in birds. PLoS ONE. 2014;9:e89955.

Estrela FN, Guimarães ATB, Araújo APDC, Silva FG, Luz TMD, Silva AM, et al. Toxicity of polystyrene nanoplastics and zinc oxide to mice. Chemosphere. 2021;271:129476.

Fisher SA, Bortolotti GR, Fernie KJ, Smits JE, Marchant TA, Drouillard KG, et al. Courtship behavior of captive American kestrels ( Falco sparverius ) exposed to polychlorinated biphenyls. Arch Environ Cont Toxicol. 2001;41:215–20.

Article   CAS   Google Scholar  

Fossi MC, Panti C, Baini M, Lavers JL. A review of plastic-associated pressures: cetaceans of the Mediterranean Sea and Eastern Australian shearwaters as case studies. Front Mar Sci. 2018;5:1–10.

Frederick P, Jayasena N. Altered pairing behaviour and reproductive success in white ibises exposed to environmentally relevant concentrations of methylmercury. Proc R Soc B Biol Sci. 2011;278:1851–7.

Gall SC, Thompson RC. The impact of debris on marine life. Mar Pollut Bull. 2015;92:170–9.

Geyer R, Jambeck JR, Law KL. Production, use, and fate of all plastics ever made. Sci Adv. 2017;3:1700782.

Gregory MR. Environmental implications of plastic debris in marine settings—entanglement, ingestion, smothering, hangers-on, hitch-hiking and alien invasions. Philos Trans R Soc Lond B. 2009;364:2013–25.

Hammer S, Nager RG, Johnson PCD, Furness RW, Provencher JF. Plastic debris in great skua ( Stercorarius skua ) pellets corresponds to seabird prey species. Mar Pollut Bull. 2016;103:206–10.

Hanson HE, Mathews NS, Hauber ME, Martin LB. The house sparrow in the service of basic and applied biology. eLife. 2020;9:e52803.

Hao Y, Zheng S, Wang P, Sun H, Matsiko J, Li W, et al. Ecotoxicology of persistent organic pollutants in birds. Environ Sci Process Impacts. 2021;23:400–16.

Hermabessiere L, Dehaut A, Paul-Pont I, Lacroix C, Jezequel R, Soudant P, et al. Occurrence and effects of plastic additives in marine environments and organisms: a review. Chemosphere. 2017;182:781–93.

Hirai H, Takada H, Ogata Y, Yamashita R, Mizukawa K, Saha M, et al. Organic micropollutants in marine plastics debris from the open ocean and remote and urban beaches. Mar Pollut Bull. 2011;62:1683–92.

Hou JY, Lei ZM, Cui LL, Hou Y, Yang L, An R, et al. Polystyrene microplastics lead to pyroptosis and apoptosis of ovarian granulosa cells via NLRP3/Caspase-1 signaling pathway in rats. Ecotoxicol Environ Saf. 2021;212:112012.

Houston DC, Mee A, McGrady M, Warkentin IG. Why do condors and vultures eat junk? the implications for conservation. J Raptor Res. 2007;41:235–8.

Jambeck JR, Geyer R, Wilcox C, Siegler TR, Perryman M, Andrady A, et al. Marine pollution. Plastic waste inputs from land into the ocean. Science. 2015;347:768–71.

Jamieson AJ, Brooks LSR, Reid WDK, Piertney SB, Narayanaswamy BE, Linley TD. Microplastics and synthetic particles ingested by deep-sea amphipods in six of the deepest marine ecosystems on Earth. R Soc Open Sci. 2019;6:180667.

Jayasena N, Frederick PC, Larkin IL. Endocrine disruption in white ibises ( Eudocimus albus ) caused by exposure to environmentally relevant levels of methylmercury. Aquat Toxicol. 2011;105:321–7.

Jin YX, Lu L, Tu WQ, Luo T, Fu ZW. Impacts of polystyrene microplastic on the gut barrier, microbiota and metabolism of mice. Sci Total Environ. 2019;649:308–17.

Jin HB, Ma T, Sha XX, Liu ZY, Zhou Y, Meng XN, et al. Polystyrene microplastics induced male reproductive toxicity in mice. J Hazard Mater. 2021;401:123430.

Juárez R, Chacón-Madrigal E, Sandoval L. Urbanization has opposite effects on the territory size of two passerine birds. Avian Res. 2020;11:11.

Karami A, Romano N, Galloway T, Hamzah H. Virgin microplastics cause toxicity and modulate the impacts of phenanthrene on biomarker responses in African catfish ( Clarias gariepinus ). Environ Res. 2016;151:58–70.

Kashiwada S. Distribution of nanoparticles in the see-through medaka ( Oryzias latipes ). Environ Health Persp. 2006;114:1697–702.

Kramar DE, Carstensen B, Prisley S, Campbell J. Mercury concentrations in blood and feathers of nestling Bald Eagles in coastal and inland Virginia. Avian Res. 2019;10:3.

Lavers JL, Bond AL, Hutton I. Plastic ingestion by flesh-footed shearwaters ( Puffinus carneipes ): implications for fledgling body condition and the accumulation of plastic-derived chemicals. Environ Pollut. 2014;187:124–9.

Lavers JL, Sharp PB, Stuckenbrock S, Bond AL. Entrapment in plastic debris endangers hermit crabs. J Hazard Mater. 2020;387:121703.

Li PC, Li XN, Du ZH, Wang H, Yu ZR, Li JL. Di (2-ethyl hexyl) phthalate (DEHP)-induced kidney injury in quail ( Coturnix Japonica ) via inhibiting HSF1/HSF3-dependent heat shock response. Chemosphere. 2018;209:981–8.

Li M, Zhu WW, Wang Y, Sun YF, Li JY, Liu XL, et al. Effects of capture and captivity on plasma corticosterone and metabolite levels in breeding Eurasian Tree Sparrows. Avian Res. 2019;10:16.

Li L, Ge JR, Zheng SY, Hong LH, Zhang XN, Li M, et al. Thermogenic responses in Eurasian Tree Sparrow ( Passer montanus ) to seasonal acclimatization and temperature-photoperiod acclimation. Avian Res. 2020;11:35.

Li M, Nabi G, Sun YF, Wang Y, Wang LM, Jiang C, et al. The effect of air pollution on immunological, antioxidative and hematological parameters, and body condition of Eurasian tree sparrows. Ecotoxicol Environ Saf. 2021;208:111755.

Lindborg VA, Ledbetter JF, Walat JM, Moffett C. Plastic consumption and diet of glaucous-winged gulls ( Larus glaucescens ). Mar Pollut Bull. 2012;64:2351–6.

Lu L, Wan ZQ, Luo T, Fu ZW, Jin YX. Polystyrene microplastics induce gut microbiota dysbiosis and hepatic lipid metabolism disorder in mice. Sci Total Environ. 2018;631–632:449–58.

MacLeod M, Arp HPH, Tekman MB, Jahnke A. The global threat from plastic pollution. Science. 2021;373:61–5.

Marín-Gómez OH, García-Arroyo M, Sánchez-Sarria CE, Sosa-López JR, Santiago-Alarcon D, MacGregor-Fors I. Nightlife in the city: drivers of the occurrence and vocal activity of a tropical owl. Avian Res. 2020;11:9.

Mattsson K, Ekvall MT, Hansson LA, Linse S, Malmendal A, Cedervall T. Altered behavior, physiology, and metabolism in fish exposed to polystyrene nanoparticles. Environ Sci Technol. 2015;49:553–61.

Mattsson K, Adolfsson K, Ekvall MT, Borgström MT, Linse S, Hansson LA, et al. Translocation of 40 nm diameter nanowires through the intestinal epithelium of Daphnia magna . Nanotoxicology. 2016;10:1160–7.

Mattsson K, Johnson EU, Malmendal A, Linse S, Hansson LA, Cedervall T. Brain damage and behavioural disorders in fish induced by plastic nanoparticles delivered through the food chain. Sci Rep. 2017;7:11452.

McCarty JP, Second AL. Possible effects of PCB contamination on female plumage color and reproductive success in Hudson River Tree Swallows. Auk. 2000;117:987–95.

McNab BK. Ecological factors affect the level and scaling of avian BMR. Comp Biochem Physiol A Mol Integr Physiol. 2009;152:22–45.

Moore CJ. Synthetic polymers in the marine environment: a rapidly increasing, long-term threat. Environ Res. 2008;108:131–9.

Munshi-South J, Wilkinson GS. Bats and birds: exceptional longevity despite high metabolic rates. Ageing Res Rev. 2010;9:12–9.

Nabi G, Ali M, Khan S, Kumar S. The crisis of water shortage and pollution in Pakistan: risk to public health, biodiversity, and ecosystem. Environ Sci Pollut Res. 2019;26:10443–5.

Nabi G, Wang Y, Lü L, Jiang C, Ahmad S, Wu YF, et al. Bats and birds as viral reservoirs: a physiological and ecological perspective. Sci Total Environ. 2021;754:142372.

Napper IE, Davies BFR, Clifford H, Elvin S, Koldewey HJ, Mayewski PA, et al. Reaching new heights in plastic pollution—preliminary findings of microplastics on mount everest. One Earth. 2020;3:621–30.

Nelms SE, Barnett J, Brownlow A, Davison NJ, Deaville R, Galloway TS, et al. Microplastics in marine mammals stranded around the British coast: ubiquitous but transitory? Sci Rep. 2019;9:1075.

O’Shea TJ, Stafford CJ. Phthalate plasticizers: accumulation and effects on weight and food consumption in captive starlings. Bull Environ Contam Toxicol. 1980;25:345–52.

Orme CDL, Davies RG, Olson VA, Thomas GH, Ding TS, Rasmussen PC, et al. Global patterns of geographic range size in birds. PLoS Biol. 2006;4:e208.

Ottinger MA, Quinn MJ Jr, Lavoie E, Abdelnabi MA, Thompson N, Hazelton JL, et al. Consequences of endocrine disrupting chemicals on reproductive endocrine function in birds: establishing reliable end points of exposure. Domest Anim Endocrinol. 2005;29:411–9.

Ottinger MA, Lavoie E, Thompson N, Barton A, Whitehouse K, Barton M, et al. Neuroendocrine and behavioral effects of embryonic exposure to endocrine disrupting chemicals in birds. Brain Res Rev. 2008;57:376–85.

Patrício Silva AL, Prata JC, Walker TR, Duarte AC, Ouyang W, Barcelò D, et al. Increased plastic pollution due to COVID-19 pandemic: challenges and recommendations. Chem Eng J. 2021;405: 126683.

Pierce KE, Harris RJ, Larned LS, Pokras MA. Obstruction and starvation associated with plastic ingestion in a northern gannet morus bassanus and a greater shearwater Puffinus Gravis . Mar Ornithol. 2004;32:187–9.

Plaza PI, Blanco G, Madariaga J, Boeri E, Teijeiro ML, Bianco G, et al. Scavenger birds exploiting rubbish dumps: pathogens at the gates. Transbound Emerg Dis. 2018;2019(66):873–81.

Provencher JF, Bond AL, Avery Gomm S, Borrelle SB, Bravo Rebolledo EL, Hammer S, et al. Quantifying ingested debris in marine megafauna: a review and recommendations for standardization. Anal Methods. 2017;9:1454–69.

Prüst M, Meijer J, Westerink RHS. The plastic brain: neurotoxicity of micro- and nanoplastics. Part Fibre Toxicol. 2020;17:24.

Puskic P, Lavers JL, Adams LA, Grünenwald M, Hutton I, Bond AL. Uncovering the sub-lethal effects of plastic ingestion by shearwaters using fatty acid analysis. Conserv Physiol. 2019;7:coz017.

Rapp DC, Youngren SM, Hartzell P, David HK. Community-wide patterns of plastic ingestion in seabirds breeding at French frigate shoals, northwestern Hawaiian islands. Mar Pollut Bull. 2017;123:269–78.

Rathi A, Basu S, Barman S. Adsorptive removal of fipronil from its aqueous solution by modified zeolite HZSM-5: equilibrium, kinetic and thermodynamic study. J Mol Liq. 2019;283:867–78.

Reddy AVB, Moniruzzaman M, Aminabhavi TM. Polychlorinated biphenyls (PCBs) in the environment: recent updates on sampling, pretreatment, cleanup technologies and their analysis. Chem Eng J. 2019;358:1186–207.

Revel M, Châtel A, Mouneyrac C. Micro(nano)plastics: a threat to human health? Curr Opin Environ Sci Health. 2018;1:17–23.

Reynolds C, Ryan PG. Micro-plastic ingestion by waterbirds from contaminated wetlands in South Africa. Mar Pollut Bull. 2018;126:330–3.

Ribeira F, Garcia AR, Pereira BP, Fonseca M, Mestre NC, Fonseca TG, et al. Microplastics effects on Scrobicularia plano . Mar Pollut Bull. 2017;122:379–91.

Rideout BA, Stalis I, Papendick R, Pessier A, Puschner B, Finkelstein ME, et al. Patterns of mortality in free-ranging California Condors ( Gymnogyps californianus ). J Wildl Dis. 2012;48:95–112.

Rochman CM, Browne MA, Halpern BS, Hentschel BT, Hoh E, Karapanagioti HK, et al. Policy: classify plastic waste as hazardous. Nature. 2013;494:169–71.

Rochman CM, Kurobe T, Flores I, Teh SJ. Early warning signs of endocrine disruption in adult fish from the ingestion of polyethylene with and without sorbed chemical pollutants from the marine environment. Sci Total Environ. 2014;493:656–61.

Rodríguez A, Rodríguez B, Carrasco MN. High prevalence of parental delivery of plastic debris in Cory’s shearwaters ( Calonectris diomedea ). Mar Pollut Bull. 2012;64:2219–23.

Roman L, Lowenstine L, Parsley LM, Wilcox C, Hardesty BD, Gilardi K, et al. Is plastic ingestion in birds as toxic as we think? Insights from a plastic feeding experiment. Sci Total Environ. 2019;665:660–7.

Ryan PG. Entanglement of birds in plastics and other synthetic materials. Mar Pollut Bull. 2018;135:159–64.

Sánchez R, Sánchez J, Oria J, Guil F. Do supplemental perches influence electrocution risk for diurnal raptors? Avian Res. 2020;11:20.

Sanderson JT, Elliott JE, Norstrom RJ, Whitehead PE, Hart LE, Cheng KM, et al. Monitoring biological effects of polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls in Great Blu Heron Chicks ( Ardea herodias ) in British Columbia. J Toxicol Environ Health. 1994;41:435–50.

Sletten S, Bourgeon S, Badsen BJ, Herzke D, Criscuolo F, Massemin S, et al. Organohalogenated contaminants nestlings: An assessment of relationships to immunoglobulin levels, telomeres and oxidative stress. Sci Total Environ. 2016;539:337–49.

Sun YF, Ren Z, Wu YF, Lei FM, Dudley R, Li DM. Flying high: limits to flight performance by sparrows on the Qinghai-Tibet Plateau. J Exp Biol. 2016;219:3642–8.

PubMed   Google Scholar  

Susanti NK, Mardiastuti A, Wardiatno Y. Microplastics and the impact of plastic on wildlife: a literature review. Environ Earth Sci. 2020;528:012013.

Tanaka K, Takada H, Yamashita R, Mizukawa K, Fukuwaka M, Watanuki Y. Accumulation of plastic-derived chemicals in tissues of seabirds ingesting marine plastics. Mar Pollut Bull. 2013;69:219–22.

Tanaka K, Watanuki Y, Takada H, Ishizuka M, Yamashita R, Kazama M, et al. In vivo accumulation of plastic-derived chemicals into seabird tissues. Curr Biol. 2020;30:723–8.

Tauler-Ametlller H, Pretus JL, Hernández-Matías A, Ortiz-Santaliestra ME, Mateo R, Real J. Domestic waste disposal sites secure food availability but diminish plasma antioxidants in Egyptian vulture. Sci Total Environ. 2019;650:1382–91.

Teuten EL, Saquing JM, Knappe DRU, Barlaz MA, Jonsson S, Björn A, et al. Transport and release of chemicals from plastics to the environment and to wildlife. Philos Trans R Soc B. 2009;364:2027–45.

Verlis KM, Campbell ML, Wilson SP. Ingestion of marine debris plastic by the wedge-tailed shearwater Ardenna pacifica in the Great Barrier Reef, Australia. Mar Pollut Bull. 2013;72:244–9.

von Moos N, Burkhardt-Holm P, Kohler A. Uptake and effects of microplastics on cells and tissue of the blue mussel Mytilus edulis L. after an experimental exposure. Environ Sci Technol. 2012;46:11327–35.

Waring RH, Harris RM, Mitchell SC. Plastic contamination of the food chain: a threat to human health? Maturitas. 2018;115:64–8.

Wilcox C, Van Sebille E, Hardesty BD. Threat of plastic pollution to seabirds is global, pervasive, and increasing. Proc Natl Acad Sci USA. 2015;112:11899–904.

Wright SL, Thompson RC, Galloway TS. The physical impacts of microplastics on marine organisms: a review. Environ Pollut. 2013;178:483–92.

Yamashita R, Takada H, Fukuwaka MA, Watanuki Y. Physical and chemical effects of ingested plastic debris on short-tailed shearwaters, Puffinus tenuirostris , in the North Pacific Ocean. Mar Pollut Bull. 2011;62:2845–9.

Yang Y, Zhang YM, Ding J, Ai SW, Guo R, Bai XJ. Optimal analysis conditions for sperm motility parameters with a CASA system in a passerine bird Passer montanus . Avian Res. 2019;10:35.

Yang Y, Zhang W, Wang S, Zhang H, Zhang Y. Response of male reproductive function to environmental heavy metal pollution in a free-living passerine bird, Passer montanus . Sci Total Environ. 2020;747:141402.

Yin L, Chen B, Xia B, Shi X, Qu K. Polystyrene microplastics alter the behavior, energy reserve and nutritional composition of marine jacopever ( Sebastes schlegelii ). J Hazard Mater. 2018;360:97–105.

Yin L, Liu H, Cui H, Chen B, Li L, Wu F. Impacts of polystyrene microplastics on the behavior and metabolism in a marine demersal teleost, black rockfish ( Sebastes schlegelii ). J Hazard Mater. 2019;380:120861.

Young LC, Vanderlip C, Duffy DC, Afanasyev V, Shaffer SA. Bringing home the trash: do colony-based differences in foraging distribution lead to increased plastic ingestion in Laysan albatrosses? PLoS ONE. 2009;4:e7623.

Yu LH, Luo XJ, Liu HY, Zeng YH, Zheng XB, Wu JP, et al. Organohalogen contamination in passerine birds from three metropolises in China: geographical variation and its implication for anthropogenic effects on urban environments. Environ Pollut. 2014;188:118–23.

Zhang YZ, Zuo YZ, Du ZH, Xia J, Zhang C, Wang H, et al. Di (2-ethylhexyl) phthalate (DEHP)-induced hepatotoxicity in quails ( Coturnix Japonica ) via triggering nuclear xenobiotic receptors and modulating cytochrome P450 systems. Food Chem Toxicol. 2018;120:287–93.

Zhao S, Zhu L, Li D. Microscopic anthropogenic litter in terrestrial birds from Shanghai, China: not only plastics but also natural fibers. Sci Total Environ. 2016;550:1110–5.

Zhu D, Bi QF, Xiang Q, Chen QL, Christie P, Ke X, et al. Trophic predator-prey relationships promote transport of microplastics compared with the single Hypoaspis aculeifer and Folsomia candida . Environ Pollut. 2018;235:150–4.

Zhu YG, Zhu D, Xu T, Ma J. Impacts of (micro) plastics on soil ecosystem: progress and perspective. J Agro-Environ Sci. 2019;38:1–6.

CAS   Google Scholar  

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This work was supported by the National Natural Science Foundation of China (NSFC, 31971413) and the Natural Science Foundation of Hebei Province (NSFHB, C2020205038) to DL; the NSFHB (C2020205005), the Foundation of Hebei Normal University (17116027), and the Postdoctoral Research Foundation of China (PRFC, 2020M670685) to LW; the PRFC (2020M680902) to LY.

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Wang, L., Nabi, G., Yin, L. et al. Birds and plastic pollution: recent advances. Avian Res 12 , 59 (2021). https://doi.org/10.1186/s40657-021-00293-2

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How evolution has optimized the magnetic sensor in birds

by Ute Kehse, Carl von Ossietzky-Universität Oldenburg

Migratory birds are able to navigate and orientate with astonishing accuracy using various mechanisms, including a magnetic compass. A team led by biologists Dr. Corinna Langebrake and Prof. Dr. Miriam Liedvogel from the University of Oldenburg and the Institute of Avian Research "Vogelwarte Helgoland" in Wilhelmshaven has now compared the genomes of several hundred bird species and found further evidence that a specific protein in the birds' eyes is the magnetoreceptor which underlies this process.

The researchers found that there have been significant evolutionary changes in the gene that encodes the protein cryptochrome 4 and that certain groups of birds have lost it entirely.

These findings are indicative of adaptation to varying environmental conditions and support the theory that cryptochrome 4 functions as a sensor protein.

The study was prompted by research at the Universities of Oldenburg and Oxford (UK), which has shown that magnetoreception is based on a complex quantum mechanical process that takes place in certain cells in the retinas of migratory birds .

In a paper published in the journal Nature in 2021, the German-British team presented findings according to which it was highly likely that cryptochrome 4 was the magnetoreceptor they had been looking for: first, they were able to prove that the protein is present in the birds' retina, and second, both experiments with bacterially produced proteins and model calculations showed that cryptochrome 4 exhibits the suspected quantum effect in response to magnetic fields.

Interestingly, the research also demonstrated that these proteins are significantly more sensitive to magnetic fields in robins, which are migratory birds, than in chickens and pigeons, which are resident species.

"Consequently, the reason why cryptochrome 4 is more sensitive in robins than in chickens and pigeons must be found in the protein's DNA sequence," says Langebrake, who was the lead author. "The sequence was probably optimized by evolutionary processes in these nocturnal migratory birds."

In the current study, the team led by Langebrake and Liedvogel, therefore, investigated magnetoreception from an evolutionary perspective for the first time. The researchers analyzed the cryptochrome 4 genes of 363 bird species ranging from the little spotted kiwi to the song sparrow.

First, they compared the protein's evolutionary rate with that of two related cryptochromes and found that the gene sequences of the cryptochromes used for comparison were very similar across all bird species: They appear to have changed very little over the course of evolution. This is most likely due to their key role in regulating the internal clock—a mechanism that is essential for all birds and in which modifications would have extremely negative effects.

Cryptochrome 4, by contrast, proved to have been highly variable. "This suggests that the protein is important for adaptation to specific environmental conditions," explains Liedvogel, who is Professor of Ornithology at the University of Oldenburg and director of the Institute of Avian Research. The resulting specialization could be magnetoreception. "A similar pattern has been observed in other sensory proteins such as light-sensitive pigments in the eye," she explains.

The researchers then took a closer look at how the gene sequence for chryptochrome 4 has evolved in the evolutionary history of birds. The results led the scientists to conclude that, in particular, in the case of the passerine (Passeriformes) order, the protein has been optimized through rapid selection. "Our results indicate that evolutionary processes could have led to cryptochrome 4 specializing as a magnetoreceptor in songbirds," says Langebrake.

Another interesting finding was that in three clades of tropical birds—parrots, hummingbirds, and Tyranni (Suboscines), also known as tyrants—the information for cryptochrome 4 has been lost in the evolutionary process, meaning that these birds are unable to produce the protein. This indicates that it does not play a vital role in their survival. However, while parrots and hummingbirds are sedentary, some tyrants are long-distance migrants who, like small European songbirds, fly both during the day and at night.

"The fact that, unlike robins, they do not have cryptochrome 4 makes them an ideal system for investigating various hypotheses about magnetoreception," says Langebrake.

An interesting question here is: have the Tyranni developed a magnetic sense that works independently of cryptochrome 4? Or are they able to orientate themselves without a magnetic sense?

Another possibility is that their magnetic sense has the same characteristics as that in robins, which is light-dependent and can be disrupted by radio waves, for example. "The first two scenarios would strongly corroborate the cryptochrome 4 hypothesis, while the third would pose a problem for the theory," the biologist emphasizes.

As a next step, the research team is therefore planning to investigate magnetic orientation in Tyranni and clarify whether or not they have a magnetic sense. "The Tyranni clade provides us with a natural tool for understanding the function of cryptochrome 4 and the importance of magnetoreception in migratory birds," says Liedvogel, outlining a starting point for further research.

The research is published in the journal Proceedings of the Royal Society B: Biological Sciences .

Journal information: Proceedings of the Royal Society B , Nature

Provided by Carl von Ossietzky-Universität Oldenburg

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Volume 2 Supplement 2

Special Issue: Transitional Fossils

• Original Scientific Articles
• Open access
• Published: 16 April 2009

Downsized Dinosaurs: The Evolutionary Transition to Modern Birds

• Luis M. Chiappe 1  

Evolution: Education and Outreach volume  2 ,  pages 248–256 ( 2009 ) Cite this article

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Living birds are the most diverse land vertebrates and the heirs of a rich chapter in the evolution of life. The origin of modern birds from animals similar to Tyrannosaurus rex is among the most remarkable examples of an evolutionary transition. A wealth of recently discovered fossils has finally settled the century-old controversy about the origin of birds and it has made the evolutionary saga toward modern birds one of the best documented transitions in the history of life. This paper reviews the evidence in support of the origin of birds from meat-eating dinosaurs, and it highlights the array of fossils that connect these fearsome animals with those that fly all around us.

With nearly 10,000 living species, birds are the most diverse land vertebrates and are the product of a long and fascinating chapter in the evolution of life. The origin of modern birds is undoubtedly one of the most dramatic examples of an evolutionary transition—one connecting animals akin to the fearsome Tyrannosaurus rex with the feathered marvels we now see all around us—a transformation documented by a wealth of intermediate fossils that date back to the Mesozoic Era (Chiappe 2007 ), the geologic period that spanned between 245 and 65 million years ago. The importance of the fossil record in providing evidence of intermediate stages in an evolutionary transition has long been recognized (Sues and Anderson 2007 ). Fossils provide chronological information about milestones within a transition, they help us visualize the sequence of physical transformations involved in it, and they document a series of intermediate characteristics that are no longer present (or that are highly modified) in extant organisms. Fossils also document that the origin of any major group is accompanied by a wide range of evolutionary experimentation in which closely related lineages—whether contemporaneous or not—approach to a greater or lesser degree the characteristic trademarks of the new group. A wealth of intermediate fossils has made the evolutionary saga toward modern birds one of the best documented transitions in the history of life (Fig.  1 ).

The skeletons of the nonavian maniraptoran Velociraptor , the Jurassic bird Archaeopteryx , the Early Cretaceous short-tailed bird Sapeornis and enantiornithine Longipteryx , the Late Cretaceous Ichthyornis , and the living Gallus (chicken). In recent years, a wealth of bird-like nonavian maniraptorans and primitive (“dinosaur”-like) birds have been unearthed from Mesozoic rocks worldwide—these discoveries have consolidated the notion that birds evolved from maniraptoran theropod dinosaurs. Drawings not to scale

Birds have an ancient and enormously rich history. The common ancestor of all living groups of birds can be traced to at least the Late Cretaceous period, more than 75 million years ago, and the earliest records of fossils widely accepted as birds—those of the famed Archaeopteryx from southern Germany—date back twice as far. Deciphering the origin of birds, namely, identifying the closest relatives to the most recent common ancestor of Archaeopteryx and modern birds, has been a matter of scientific debate and scrutiny throughout the history of evolutionary biology (Chiappe 2007 ; Witmer 1991 ; Chatterjee 1997 ; Shipman 1998 ; Feduccia 1999 ). As early as the eighteenth century, birds were generally placed immediately ahead of flying fishes in the “chains of being” postulated by the naturalists of that time. With the nineteenth century's advent of evolutionary thinking, especially after Darwin's theory of evolution by natural selection, more explicit hypotheses of relationships were formulated. Post-Darwinian times witnessed a diversity of hypotheses in which birds were considered to be most closely related to a variety of extinct and extant lineages of reptiles. These hypotheses related birds to groups of animals such as turtles, crocodiles, and their relatives, various primitive Triassic fossils (245 to 208 million years ago), pterodactyls, and their kin, and the plant-eating ornithischians and the meat-eating theropod dinosaurs. For decades, the origin of birds remained obscure and controversial—the fossil record was too fragmentary to provide a clear picture. Today, however, most of the other hypothetical relationships have been abandoned and the theropod hypothesis has received nearly universal acceptance (Shipman 1998 ; Rowe et al. 1998 ; Sereno 1999 ; Chiappe and Witmer 2002 ). In fact, because birds are overwhelmingly interpreted as the descendants of a group of carnivorous dinosaurs, most scientists argue that they be considered living dinosaurs. Therefore, birds are today interpreted as avian dinosaurs— Velociraptor , Tyrannosaurus , Brachiosaurus , and all other traditional “dinosaurs” that coexisted with a variety of primitive Mesozoic birds are referred to as nonavian dinosaurs.

Birds as Living Dinosaurs

The idea that the ancestry of birds can be traced back to a group of carnivorous dinosaurs called theropods is not new (Chiappe 2007 ). Nearly 150 years ago, soon after the publication of Darwin's Origin of Species , German embryologist C. Gegenbaur used similarities in the structure of the ankle to place the small, 150-million-year-old theropod Compsognathus in an intermediate position between birds and other reptiles. At about the same time, American paleontologist E.D. Cope compared the ankle of the Jurassic theropod Megalosaurus to that of an ostrich, and on the basis of this and other skeletal similarities, argued for a close relationship of theropods and birds. Despite these initial considerations, it was British anatomist T.H. Huxley (Huxley 1868 ) who first popularized the idea that birds had originated within theropod dinosaurs. In the ensuing years, a myriad of other skeletal features supporting the dinosaurian origin of birds has been discovered in the fossils of large and small theropods. Since the 1960s, a greater understanding of small predatory dinosaurs of the Cretaceous age, such as the dromaeosaurid Deinonychus (Ostrom 1969 , 1976 ), has led to the idea that birds had originated from within a group of bird-like theropods called maniraptorans (Gauthier 1986 ). Today, the skeletons of such maniraptoran theropods such as the sickle-clawed dromaeosaurids ( Deinonychus , Velociraptor , and their kin; Fig.  1 ), the lightly built troodontids ( Troodon , Mei , and their kin), the parrot-headed oviraptorids ( Oviraptor and relatives), and the short-armed alvarezsaurids ( Mononykus and its kin) are recognized as sharing a great deal of similarity with birds (Chiappe and Witmer 2002 ; Weishampel et al. 2004 ). Not only have birds retained the bipedalism, hollowed bones, and the three fully developed toes of their theropod predecessors, but these animals also share a series of air spaces connected to the ear region, unique structures of their vertebral column and rib cage, elongate forelimbs with wrist bones allowing swivel-like movements of the hand and similar structures in the pelvis and hindlimbs, as well as many other characteristics distributed over the entire skeleton (Rowe et al. 1998 ; Sereno 1999 ; Chiappe and Witmer 2002 ; Weishampel et al. 2004 ; Novas and Puerta 1997 ; Holtz 1998 ). Indeed, many skeletal features previously thought to be exclusively avian—such as wishbones, laterally facing wingpits, and large breastbones—have now been discovered among nonavian maniraptorans (Padian and Chiappe 1998 ).

In recent years, a wealth of evidence taken from comparisons between the skeletons of these dinosaurs and those of birds has been supplemented by diverse lines of evidence in support of the same evolutionary relationship. Paleontologists have determined that the shape and structure of nonavian maniraptoran eggs were similar to those of living birds (Mikhailov 1992 ; Zelenitsky 2006 ; Varricchio and Jackson 2004 ; Grellet-Tinner et al. 2006 ). Some of these features involve the presence of more than one distinct crystalline layer in the eggshell (distinguished by a differential disposition of eggshell crystals), reduction in the number of airholes perforating the eggshell, a relative increase in the volume of the egg (with respect to the adult's size), and the development of asymmetrical eggs in which one pole is narrower than the other (Fig.  2 ). Snapshots of ancient behavior revealed by a handful of exceptional fossils have also provided support to the hypothesis that birds evolved from maniraptoran dinosaurs. The discovery of a “gravid” oviraptorid female containing a pair of shelled eggs inside her pelvic canal (Sato et al. 2005 ) has confirmed previous interpretations based on the spatial arrangement of eggs within clutches of nonavian maniraptorans. These clutches—particularly well known among oviraptorids—show that the eggs were arranged in pairs, as opposed to typical reptilian clutches (turtles, crocodiles, and other dinosaurs), in which the eggs lack any spatial arrangement (Grellet-Tinner et al. 2006 ) (Fig.  2 ). This evidence indicates that, as with birds, nonavian maniraptorans laid their eggs sequentially, at discrete time intervals. It probably took several days for a nonavian maniraptoran female to lay its egg clutch (Varricchio and Jackson 2004 ; Grellet-Tinner et al. 2006 ), a condition shared with birds.

Characteristics of the eggs and clutches of several nonavian maniraptorans support the inclusion of birds within these theropod dinosaurs. For example, the presence of at least two distinct crystalline layers in the eggshell and the existence of an asymmetric egg (less asymmetric among oviraptorids) can be traced back to as far as the maniraptoran divergence. The distribution of the eggs within a clutch in oviraptorids indicates that these dinosaurs laid their eggs sequentially (other evidence also indicates that, as in the case of birds, they also brooded their clutch)

Other extraordinary discoveries have shed light on the nesting behavior of these dinosaurs. Skeletons of oviraptorids (Norell et al. 1995 ; Clark et al. 1999 ) and troodontids (Varricchio and Jackson 2004 ) have been discovered on top of their clutches of eggs. The fossils show evidence that these animals adopted a posture similar to that of brooding birds. In oviraptorids, the adult tucked its legs inside an open space at the center of the egg-clutch and hugged the periphery of the clutch with its long forelimbs; in the more lightly built troodontids, the adult sat on top of the vertically buried eggs. These discoveries suggest that, regardless of its specific role (protection, incubation), typical avian nesting behaviors (adults sitting on top of their nests) were widespread among nonavian maniraptorans. Additional evidence further documents behavioral similarities with birds. Fossils of troodontids with their skeleton arranged such that the hindlimbs are flexed beneath the belly, the neck is turned backwards, and the head is tucked between the wing and the body have documented that at least some of the maniraptoran precursors of birds had already evolved stereotypical resting poses familiar to many birds (Xu and Norell 2004 ).

More specific fields of research have made their own empirical contributions in support of the dinosaurian legacy of birds. Studies of dinosaurian growth rates, based on details preserved in the fossilized tissue of their bones, have documented that these animals, once believed to be slow-growing, actually grew at speeds comparable to many living birds (Erickson et al. 2001 ), and special bone tissues, such as the medullary bone characteristic of ovulating birds, have been documented in a female T. rex (Schweitzer et al. 2005 ). Evidence in support of the evolutionary transition between nonavian dinosaurs and birds has also been uncovered from disciplines as far-off from classic paleontology as genetics. Studies correlating the sizes of bone cells and genomes (the entire genetic material of an organism) have revealed that the mighty T. rex and its fearsome kin had the small genomes typical of modern birds (Organ et al. 2007 ), and putative protein sequences from soft tissues of this dinosaur have also highlighted its evolutionary closeness to birds (Organ et al. 2008 , although for a different interpretation of this evidence, see Dalton 2008 ).

Yet, despite the multiplicity of this extensive body of evidence, nothing has cemented the dinosaurian pedigree of birds more than the realization that true feathers—the quintessential avian feature—may have covered the bodies of a variety of nonavian dinosaurs (Norell and Xu 2005 ). The enormous significance of these fossils notwithstanding, the documented existence of feathers in nonavian dinosaurs has, thus far, been limited to a dozen or so species, all of them circumscribed to the Cretaceous deposits of East Asia. Some of these dinosaurs exhibit feathers that are filament-like, with a minimal degree of branching, but a number of others display pennaceous feathers with distinct shafts and vanes. In certain nonavian maniraptorans, long pennaceous feathers attach to the distal part of the tail, either in a fan-like fashion or giving the tail the frond-like appearance common to primitive birds such as Archaeopteryx (Fig.  1 a). Long pennaceous feathers also attach to the tip of the forelimbs of some of these maniraptorans, and in the case of the peculiar dromaeosaurid Microraptor (Norell and Xu 2005 ), they form a wing of essentially modern design. Despite the evidence of plumage being restricted to a handful of nonavian dinosaurs, the fact that these fossils span a large portion of the family tree of theropods and display a great diversity of sizes, appearances, and lifestyles, hints at a much larger and yet undocumented diversity (Fig.  3 )—even the colossal T. rex may have been covered with a cloak of feathers at some early stage of its life. It is an amazing experience to gaze at the entirely modern feathers of animals, whereas their skeletal characteristics are so unquestionable dinosaurian.

Genealogical relationships of feathered nonavian theropods. Current evidence supports the hypothesis that filamentous and vaned feathers evolved with the divergence of coelurosaurs and maniraptorans, respectively

An important corollary of these discoveries is that feathers did not evolve in the context of flight. With the sole exception of Microraptor , it is certain that none of these feathered dinosaurs were able to take to the air. The forelimbs and their feathers are both much shorter than in flying birds and their bodies are larger. The evolutionary transition toward birds and the origin of their flight involved a dramatic reduction in body size. These feathered dinosaurs indicate that, at their onset, feathers must have had a different function, perhaps insulating the bodies of animals that had metabolically diverged from their cold-blooded, reptilian ancestors. My research has suggested that vaned feathers may have originated in the context of thrust, evolving in running nonavian theropods that by flapping their feathered arms were able to increase their running speed (Burgers and Chiappe 1999 ). In the end, however, we simply do not have an answer for what was the original function of feathers; nonetheless, we have been able to eliminate flight as an option.

Today, the century-old debate on bird ancestry has largely been resolved. The uncertainties that led to this long controversy—both empirical and methodological—have been clarified and there is an overwhelming consensus in support of the idea that birds evolved from maniraptoran theropods. Current evidence highlights the fact that many features previously thought to be exclusively avian—from feathers to a wishbone—have now been discovered in the immediate dinosaur predecessor of birds. The origin of birds was also preceded by a substantial reduction in body size—the most primitive members of groups such as troodontids and dromaeosaurids are smaller than one meter long (Turner et al. 2007 ). This notable reduction in the size of the forebears of birds was an important prerequisite of flight; even this most characteristic avian attribute is likely to have been inherited by birds from their dinosaurian predecessors.

The comparative studies that have been the building blocks of these important evolutionary conclusions have been greatly assisted by many newly discovered Mesozoic-aged birds (Chiappe 2007 ), which by possessing many skeletal features that are only slightly modified from the ancestral maniraptoran condition, fill a critical gap in the evolutionary transition toward modern birds (Figs.  1 , 4 , and 5 ). This newly-discovered fossil menagerie has unveiled an unexpected diversity of archaic birds that would take birding to another dimension. These new discoveries are reviewed next.

Cladogram or diagram depicting the genealogical relationships among the main lineages of premodern birds and some lineages of nonavian maniraptoran dinosaurs. The known fossil record of these groups is also highlighted. The concept of a dove as a living dinosaur—because they share a common descent—may seem bizarre, but, in reality, it is just as logical as the argument that humans are primates because we evolved from primates

Photographs of the Berlin specimen of the Late Jurassic Archaeopteryx ( a ), the Early Cretaceous short-tailed bird Confuciusornis ( b ), long-tailed bird Jeholornis ( c ), enantiornithine Eoenantiornis ( d ), and primitive ornithuromorph Yanornis ( e ). Photographs not to scale

The Long March Toward Modern Birds

Research on the early history of birds and the development of flight has been at the forefront of paleontology since the advent of evolutionary thought. For most of this time, however, the available evidence was limited to a small number of fossils largely restricted to near-shore and marine environments and was greatly separated both anatomically and in time. In the last few decades, however, our understanding of the origin and ancient divergences of birds has advanced at an unparalleled rate. This rapid increase in discoveries has not only filled much of the anatomical and temporal gaps that existed previously, but has also made the study of early birds one of the most dynamic fields of vertebrate paleontology.

New information highlights the fact that the enormous diversity of living birds is just a remnant of an archaic evolutionary radiation that can be traced back to Archaeopteryx (Mayr et al. 2005 ) (Figs.  1 and 4 ). Few physical features set this most ancient bird apart from its theropod dinosaur predecessors. However, Archaeopteryx gives us paramount clues to the beginning of one of the most dramatic evolutionary events in the history of vertebrates—the development of powered flight in birds. This 150-million-year-old jay-sized bird with toothed jaws, clawed wings, and a long bony tail stands alone in the fossil record of birds of the end of the Jurassic period. Yet, in the last decade, a large number and variety of birds have been found in early Cretaceous rocks ranging from 130 to 115 million years ago (Chiappe 2007 ; Zhou 2004 ). These fossils reveal that a great diversity of birds with long bony tails preceded the evolution of birds with an abbreviated bony tail (Forster et al. 1998 ; Zhou and Zhang 2003 ), one composed of fewer vertebrae ending in a bony stump called a pygostyle (the structure that supports the “parson's nose”). Characteristics of the plumage, the large wing size, and specific features of their brain all suggest that Archaeopteryx and the remaining long-tailed birds were fliers, even if these birds probably required a take-off run to become airborne (Burgers and Chiappe 1999 ).

A rich diversity of more advanced birds is also recorded in these early Cretaceous rocks. In fact, the differing design of skulls, teeth, wings, and feet indicate that, even at this early phase of their evolutionary history, birds had specialized into a variety of ecological niches, including seed-feeders, insect-feeders, fish-eaters, and meat-eaters (Chiappe 2007 ). At the same time, a host of novel features of the wings, shoulders, and tails suggests that, soon after Archaeopteryx , birds evolved flying abilities not very different from the ones that amaze us today, a feat that was most likely the recipe for their dramatic diversification during the Cretaceous. Paramount among these transformations is the abbreviation of the tail and the consequent development of a pygostyle. Yet, the details of this evolutionary transition are far from clear. One recent fossil that has shed some light onto this transition is the tiny, 125-million-year-old Zhongornis (Gao et al. 2008 ) from northeastern China. Zhongornis is the first bird discovered that has a short tail and a corresponding reduced number of tail vertebrae, yet lacks the pygostyle that is present in all other short-tailed birds. Therefore, Zhongornis represents an intermediate stage between the primitive long-tailed birds and those with a bony stump at the end of the tail. Evidence from the skeleton of Zhongornis suggests that a short tail with a reduced number of vertebrae evolved earlier in birds than did the pygostyle.

Very early in their evolutionary history, short bony-tailed birds blossomed in a range of shapes and sizes. Hundreds of specimens of the stout-beaked Confuciusornis , many surrounded by a halo of dark feathers, have been unearthed from the 125-million-year-old deposits of northeastern China (Chiappe et al. 1999 ) (Fig.  5 ). This crow-sized bird sported long hands with enormous claws and long and tapering wings. Growth series of Confuciusornis spanning a large spectrum of sizes suggest that, unlike modern birds, this and other archaic birds required multiple years to reach adult size (Chiappe 2007 ). The contemporaneous and much larger Sapeornis had longer and narrower wings, superficially resembling those of albatrosses (Zhou and Zhang 2002 ) (Fig.  1 ). Albeit bearing stout teeth and a very primitive shoulder, the anatomy of this bird suggests a closer relationship to modern birds than Confuciusornis . Combined, however, these fossils best illustrate the anatomy and appearance of the most primitive short-tailed birds, which, by virtue of their proportionally larger wings, were likely better fliers than their long-tailed predecessors.

Fossils of more advanced birds are also first recorded at around 130 million years ago. Among these are the enantiornithines (Chiappe 2007 ; Chiappe and Witmer 2002 ), a group that constitutes the most important evolutionary radiation of premodern birds. Like most early birds, the majority of enantiornithines had toothed jaws and partially clawed wings (Figs.  1 and 5 ). Yet their skeletons show a series of key transformations that approach those of today's birds. Some of these include the shortening of the hand and fingers as well as changes in the proportions of the wing bones and the anatomy of the shoulder. Furthermore, these birds evolved important innovations in their plumage, namely, a safety device called the alula (a small tuft of feathers also known as the “bastard wing”), which assists modern birds during their take-off and landing (Sanz et al. 1996 ). The significant transformations of the skeleton and plumage of these birds suggest that, even at the onset of their evolutionary history, enantiornithines were able to take-off from a standstill position and maneuver in ways similar to those seen among living birds. It is most likely that the evolution of these enhanced flying capabilities played a key role in the evolutionary success of the enantiornithines, which by about 120 million years ago seem to have risen to dominance.

Rocks from the early Cretaceous also record a number of transitional fossils that herald the evolution of the closest relatives of modern birds (Fig.  1 ). In some respects, these primitive ornithuromorphs (Chiappe 2007 ; Chiappe and Witmer 2002 ; Zhou 2004 ; Zhou and Zhang 2005 ) resemble the enantiornithines, but their skeletons show, for the first time, clear trademarks of their living counterparts. The majority of these primitive ornithuromorphs were lightly built, flying birds, whose sizes tend to be larger than those of their contemporaneous enantiornithines. Like the latter, both their skeletons and plumage show clear evidence of enhanced aerodynamic capabilities. It is within these birds that we witness the origin of the extremely fast rates of body maturation characteristic of modern birds (Chiappe and Witmer 2002 ), which reach their full body size within a year after hatching.

As the rocks of the Cretaceous period become younger, a series of other lineages of ornithuromorphs make their debut. The hesperornithiforms—large, flightless, foot-propelled divers—first appear around 100 million years ago (Chiappe 2007 ; Chiappe and Witmer 2002 ). Albeit entirely restricted to the aquatic realm, the hesperornithiforms exhibit a rich and diverse evolutionary history spanning over 35 million years—their last representatives may have disappeared with the latest Cretaceous mass extinction that wiped out the last of the nonavian dinosaurs. Despite the fact that their earliest records represent birds the size of a loon, millions of years later, these supreme fish-eaters would be crowned kings of the aquatic birds with a number of large forms such as the tiny-winged, four-foot long Hesperornis and Asiahesperornis . The hesperornithiforms swam the waters of tropical seas that, during the late Cretaceous, divided in half both North America and Eurasia. On the shore of these shallow seas, over herds of duck-billed and other kinds of dinosaurs, soared the tern-sized Ichthyornis (Clarke 2004 ) (Fig.  1 ). In most respects, this bird represents a step closer to modern birds, yet it had sharply toothed jaws designed to catch fish. Ichthyornis is perhaps the best-known, closest relative of modern birds; other late Cretaceous fossils seemingly close to the latter are known by much more fragmentary remains.

Not all the birds that lived during the Mesozoic may have looked as unfamiliar as Archaeopteryx , Confuciusornis , and Hesperornis . The early representatives of today's lineages of birds can also be traced back to this remote era of our geological past. In several continents, rocks from the last part of the Cretaceous period—75 to 65 million years ago—reveal the remains of early shorebirds, ducks, and other familiar birds (Kurochkin et al. 2002 ; Clarke et al. 2005 ). These discoveries indicate that a number of modern lineages had their origins prior to the end of the Mesozoic. It is unclear how these early representatives of modern birds managed to survive the devastating mass extinction of the end of the Cretaceous, but these survivors diversified soon after into a myriad of forms, which today carry the legacy of the magnificent dinosaurs that ruled the earth tens of millions of years ago.

The Dinosaur in your Backyard

In the last few decades, our understanding of the origin and subsequent evolutionary diversification of birds has advanced at an unparalleled pace. These fossil discoveries have documented the stepwise nature of one of the most fascinating evolutionary transitions, and they have filled the large gap that separated living birds from their dinosaurian predecessors. This new evidence has shown that many of the features previously considered to be avian trademarks first evolved within theropod dinosaurs.

The strength of the hypothesis that birds evolved within maniraptoran theropod dinosaurs is manifested by the convergent results of a diversity of studies within a multitude of scientific disciplines. Today, the theropod origin of birds is supported by a wealth of evidence ranging from skeletal anatomy to molecular data. This evolutionary conclusion indicates that the diverse modern birds are a branch of a much larger avian tree that diverged during the Mesozoic era and that, in turn, all these birds are but a shoot of the majestic tree of dinosaurs. This evidence has led to the realization that the jays, finches, and hummingbirds that so peacefully frequent your backyard are indeed living dinosaurs—a surviving lineage of vicious predators that ruled the terrestrial ecosystems of the Mesozoic.

Burgers P, Chiappe LM. The wing of Archaeopteryx as a primary thrust generator. Nature 1999;399:60–2. doi: 10.1038/19967 .

Article   CAS   Google Scholar  

Chatterjee S. The rise of birds: 225 million years of evolution. Baltimore: John Hopkins University Press; 1997. p. 312.

Google Scholar  

Chiappe LM. Glorified dinosaurs. New York: Wiley; 2007. p. 263.

Chiappe LM, Witmer LM. Mesozoic birds: above the heads of dinosaurs. Berkeley: University of California Press; 2002. p. 520.

Chiappe LM, Ji S, Ji Q, Norell MA. Anatomy and systematics of the Confuciosornithidae (Aves) from the Late Mesozoic of northeastern China. Bull Am Mus Nat Hist. 1999;242:1–89.

Clark JM, Norell MA, Chiappe LM. An oviraptorid skeleton from the Late Cretaceous of Ukhaa Tolgod, Mongolia, preserved in an avian-like brooding position over an oviraptorid nest. Am Mus Novit. 1999;3265:1–36.

Clarke JA. Morphology, phylogenetic taxonomy, and systematics of Ichthyornis and Apatornis (Avialae: Ornithurae). Bull Am Mus Nat Hist. 2004;286:1–179. doi: 10.1206/0003-0090(2004)286<0001:MPTASO>2.0.CO;2 .

Article   Google Scholar  

Clarke JA, Tambussi CP, Noriega JI, Erickson GM, Ketchum RA. Definitive fossil evidence for the extant avian radiation in the Cretaceous. Nature 2005;433:305–8. doi: 10.1038/nature03150 .

Article   CAS   PubMed   Google Scholar  

Dalton R. Fresh doubts over T. rex chicken link. Nature 2008;454:1035. doi: 10.1038/4541035a .

Erickson GM, Curry-Rogers K, Yerby SA. Dinosaurian growth patterns and rapid avian growth rates. Nature 2001;412:429–33. doi: 10.1038/35086558 .

Feduccia A. The origin and evolution of birds. 2nd ed. New Haven: Yale University Press; 1999. p. 466.

Forster CA, Sampson SD, Chiappe LM, Krause DW. The theropodan ancestry of birds: new evidence from the Late Cretaceous of Madagascar. Science 1998;279:1915–9. doi: 10.1126/science.279.5358.1915 .

Gao C, Chiappe LM, Meng Q, O'Connor JK, Wang X, Cheng X, et al. A new basal lineage of Early Cretaceous birds from China and its implications on the evolution of the avian tail. Palaeontology 2008;51(4):775–91. doi: 10.1111/j.1475-4983.2008.00793.x .

Gauthier JA. Saurischian monophyly and the origin of birds. In: Padian K, editor. The origin of birds and the evolution of flight. Berkeley: California Academy of Science; 1986. p. 1–55.

Grellet-Tinner G, Chiappe LM, Norell M, Bottjer D. Dinosaur eggs and nesting behaviors: their paleobiological inferences. Palaeogeogr Palaeoclimatol Palaeoecol. 2006;232:294–321. doi: 10.1016/j.palaeo.2005.10.029 .

Holtz TR Jr. A new phylogeny of the carnivorous dinosaurs. Gaia 1998;15:5–61.

Huxley TH. On the animals which are most nearly intermediate between the birds and the reptiles. Ann Mag Nat Hist. 1868;2:66–75.

Kurochkin EN, Dyke GJ, Karhu AA. A new presbyornithid bird (Aves, Anseriformes) from the Late Cretaceous of Southern Mongolia. Am Mus Novit. 2002;3386:1–11. doi: 10.1206/0003-0082(2002)386<0001:ANPBAA>2.0.CO;2 .

Mayr G, Pohl B, Peters DS. A well-preserved Archaeopteryx specimen with theropod features. Science 2005;310:1483–6. doi: 10.1126/science.1120331 .

Mikhailov KE. The microstructure of avian and dinosaurian eggshell: phylogenetic implications. Nat Hist Mus Los Angeles Cty. 1992;36:361–73.

Norell MA, Xu X. Feathered dinosaurs. Annu Rev Earth Planet Sci. 2005;33:277–99. doi: 10.1146/annurev.earth.33.092203.122511 .

Norell MA, Clark JM, Chiappe LM, Dashzeveg D. A nesting dinosaur. Nature 1995;378:774–6. doi: 10.1038/378774a0 .

Novas FE, Puerta P. New evidence concerning avian origins from the Late Cretaceous of Patagonia. Nature 1997;387:390–2. doi: 10.1038/387390a0 .

Organ CL, Shedlock AM, Pagel M, Edwards SV. Origin of avian genome size and structure in non-avian dinosaurs. Nature 2007;446:180–4. doi: 10.1038/nature05621 .

Organ CL, Schweitzer MH, Zheng W, Freimark LM, Cantley LC, Asara JM. Molecular phylogenetics of mastodon and Tyrannosaurus rex . Science 2008;320:499. doi: 10.1126/science.1154284 .

Ostrom JH. Osteology of Deinonychus antirrhopus , an unusual theropod from the lower Cretaceous of Montana. Bull Peabody Mus Nat Hist. 1969;30:1–165.

Ostrom JH. Archaeopteryx and the origin of birds. Biol J Linn Soc Lond. 1976;8:91–182. doi: 10.1111/j.1095-8312.1976.tb00244.x .

Padian K, Chiappe LM. The origin and early evolution of birds. Biol Rev Camb Philos Soc. 1998;73:1–42. doi: 10.1017/S0006323197005100 .

Rowe T, Kishi K, Merck J Jr, Colbert M. The age of dinosaurs. 3rd ed. Educational interactive multimedia on CD-ROM for Macintosh and PC computers. New York: Freeman; 1998.

Sanz JL, Chiappe LM, Perez-Moreno BP, Buscalioni AD, Moratalla J. A new Lower Cretaceous bird from Spain: implications for the evolution of flight. Nature 1996;382:442–5. doi: 10.1038/382442a0 .

Sato T, Cheng Y, Wu X, Zelenitsky DK, Hsiao Y. A pair of shelled eggs inside a female dinosaur. Science 2005;308:375. doi: 10.1126/science.1110578 .

Schweitzer MH, Wittmeyer JL, Horner JR. Gender-specific reproductive tissue in ratites and Tyrannosaurus rex . Science 2005;308:1456–60. doi: 10.1126/science.1112158 .

Sereno PC. The evolution of dinosaurs. Science 1999;284:2137–47. doi: 10.1126/science.284.5423.2137 .

Shipman P. Taking wing. New York: Simon & Schuster; 1998. p. 320.

Sues HD, Anderson JS. Introduction: studying evolutionary transitions among vertebrates. In: Sues H-D, Anderson JS, editors. Major transitions in vertebrate evolution. Bloomington: Indiana University Press; 2007. p. 1–12.

Turner AH, Pol D, Clarke JA, Erickson GM, Norell MA. A basal dromaeosaurid and size evolution preceding avian flight. Science 2007;317:1378–81. doi: 10.1126/science.1144066 .

Varricchio DV, Jackson F. Two eggs sunny-side up: reproductive physiology in the dinosaur Troodon formosus . In: Currie PJ, Koppelhus EB, Shugar MA, Wright JL, editors. Feathered dragons: studies on the transition from dinosaurs to birds. Bloomington: Indiana University Press; 2004. p. 215–33.

Weishampel DB, Dodson P, Osmólska H, editors. The Dinosauria. 2nd ed. Berkeley: University of California Press; 2004. p. 861.

Witmer LM. Perspectives on avian origins. In: Schultze H-P, Trueb L, editors. Origins of the higher groups of tetrapods: controversy and consensus. Cornell University Press: Ithaca; 1991. p. 427–66.

Xu X, Norell MA. A new troodontid dinosaur from China with avian-like sleeping posture. Nature 2004;431:838–41. doi: 10.1038/nature02898 .

Zelenitsky D. Reproductive traits of non-avian theropods. Journal of the Paleontological Society of Korea. 2006;22:209–16.

Zhou Z. The origin and early evolution of birds: discoveries, disputes and perspectives from the fossil record. Naturwissenschaften 2004;91:455–71. doi: 10.1007/s00114-004-0570-4 .

Zhou Z, Zhang F. Largest bird from the Early Cretaceous and its implications for the earliest avian ecological diversification. Naturwissenshaften 2002;89:34–8. doi: 10.1007/s00114-001-0276-9 .

Zhou Z, Zhang F. Jeholornis compared to Archaeopteryx , with a new understanding of the earliest avian evolution. Naturwissenshaften 2003;90:220–5.

Zhou Z, Zhang F. Discovery of an ornithurine bird and its implication for Early Cretaceous avian radiation. Proc Natl Acad Sci USA. 2005;102(52):18998–9002. doi: 10.1073/pnas.0507106102 .

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Chiappe, L.M. Downsized Dinosaurs: The Evolutionary Transition to Modern Birds. Evo Edu Outreach 2 , 248–256 (2009). https://doi.org/10.1007/s12052-009-0133-4

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Noise from traffic stunts growth of baby birds, study finds

Researchers also find zebra finches 20% less likely to hatch from eggs if exposed to noise pollution

Noise pollution from traffic stunts growth in baby birds, even while inside the egg, research has found.

Unhatched birds and hatchlings that are exposed to noise from city traffic experience long-term negative effects on their health, growth and reproduction, the study found.

“Sound has a much stronger and more direct impact on bird development than we knew before,” said Dr Mylene Mariette, a bird communication expert at Deakin University in Australia and a co-author of the study, published in the journal Science . “It would be wise to work more to reduce noise pollution.”

A growing body of research has suggested that noise pollution causes stress to birds and makes communication harder for them. But whether birds are already distressed at a young age because they are affected by noise, or by how noise disrupts their environment and parental care, was still unclear.

Mariette’s team routinely exposed zebra finch eggs for five days to either silence, soothing playbacks of zebra finch songs, or recordings of city traffic noises such as revving motors and cars driving past. They did the same with newborn chicks for about four hours a night for up to 13 nights, without exposing the birds’ parents to the sounds.

They noticed that the bird eggs were almost 20% less likely to hatch if exposed to traffic noise. The chicks that did hatch were more than 10% smaller and almost 15% lighter than the other hatchlings. When the team ran analyses on their red blood cells and their telomeres – a piece of DNA that shortens with stress and age – they were more eroded and shorter than their counterparts’.

The effects continued even after the chicks were no longer exposed to noise pollution, and carried over into their reproductive age four years later. The birds disturbed by noise during the early stages of their lives produced fewer than half as many offspring as their counterparts.

“We were expecting some effects, but we didn’t expect them to be so strong,” said Mariette, especially because the exposure to noise pollution was relatively mild and for only four hours a day. “It was really quite striking.”

“We generally assume, based on numerous studies, that very young birds, especially in the egg, have very poor or no sensitivity to sound,” said Robert Dooling, an animal hearing expert from the University of Maryland in the US, who was not involved in the study. But “this study raises the spectre of broad, negative, enduring effects of noise on development”.

Hans Slabbekoorn, a professor of acoustic ecology and behaviour at Leiden University in the Netherlands who was not involved in the study, said he was particularly surprised. When his team ran experiments exposing chicks and their parents to moderate noise pollution, they did not find any impact on the growth of the chicks.

Slabbekoorn speculated that changes in the behaviour of the parents – such as how they attended to their nests more – may have avoided or compensated for the negative effects of noise on the chicks.

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“I was indeed not expecting [such a] big impact necessarily,” Slabbekoorn said. It is the cumulative nature of these negative effects that may “in the end be most problematic”, he added. “Especially when noisy conditions are indeed frequent or continuous, as with birds living in noisy neighbourhoods, close to airports, or busy highways.”

His research has also found that birds at airports are exposed to such loud noise levels that they may be partially deaf.

More data is needed to pinpoint how many birds and which species these levels apply to, and it remains unclear whether it is the loudness, the pattern, the pitch, or other elements of traffic noise that disturb the young birds, or the mechanism behind the observed effects.

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"What’s the Deal With Birds?" a New Paper Asks—While Making a Point

On April 1, a strange bit of open-access scholarship appeared in the Scientific Journal of Research and Reviews : “What’s the Deal with Birds?” A worthy query by researcher Daniel Baldassarre, surely, yet to the discerning eye, there is something odd about the paper. 

For one thing, its abstract strikes an unusually ingenuous tone: “Birds are pretty weird. I mean, they have feathers. WTF? Most other animals don’t have feathers.” And the sample size—a woodpecker, a parrot, and a penguin—also seems suspiciously small. The main figure, a graph plotted along an x-axis ranging from “weird beak” to “looks like a fish,” with a red line labeled “the deal,” is a textbook example of dadaist absurdity. The prose veers wildly between academic terminology and gormless observation. “This is the first study I am aware of to attempt to quantify the deal with birds,” Baldassarre writes. “Unfortunately, the results were ambiguous, although Bayesian approaches may prove useful in the future...When presented with weird behavior, birds exhibited a multimodal response including physical aggression and duetting, both of which were repeatable across highly variable contexts.” 

Reading such a paper, one might draw the conclusion that the editors at  Scientific Journal of Research and Reviews didn’t give it close enough consideration—or any at all—before publishing the study. That’s because the SJRR is a predatory journal, designed to bilk unwary academics out of money, and Baldassarre’s paper is a joke—quite literally—at their expense. 

Predatory journals are a common scam in academic fields. They solicit manuscript submissions, charge authors exorbitant fees, and skip typical quality checks, including the gold-standard practice of peer review .  Since legitimate open-access publications like PLOS One do sometimes charge for submissions, it’s not uncommon for people to get snookered.

“They do all sort of sneaky things, like having fancy, sneaky looking websites,” Baldassarre says—even going so far as to list real scientists on their editorial boards, often without those scientists’ knowledge. Some journals are just automated money-making scams; others are a bit more hands-on at appearing legitimate. “The common denominator is that they’re not real academic, peer-reviewed journals, so anything they publish is potentially just total garbage.”

Baldasarre first had the idea to submit a joke paper in early February, when the latest in a long line of emails from one of these scam journals landed in his inbox. He slapped together the first iteration of “What’s the Deal With Birds”—a couple of paragraphs in the cursory format of a manuscript—only to see it rejected, perhaps as an obvious parody. Undaunted, he inserted some selections from an earlier legitimate paper to pad it out and resubmitted it to SJRR . “ I wanted to bring to light how these guys operate, how ridiculous the process is, and that they are not, in most cases, reviewing these works, ” he says. “ Some people who’ve been in academia for a while are in the know, but there are clearly enough people who aren’t on the up and up and are just getting scammed.”  While SJRR initially demanded a $1,700 publication fee, Baldassarre was eventually able to bargain them down to nothing. “I think they thought if they published the first one for free I’d be more willing to publish with them later,” he says. As for whether the journal is aware of the prank, Baldassarre says the world of predatory journals is so ambiguous that it’s not clear whether the people running them are even paying attention to what ’ s published. His hope, meanwhile, is that the notoriety the piece has inspired will prompt people not to publish with SJRR in the future and to be more careful of predatory journals in general.  His cause is noble, no doubt.   Yet an important question remains: What is the deal with birds? Baldassarre’s actual research involves bird behavior, and aims to discover why they do some of the strange and silly things they do. While observation and experimentation have their benefits, Baldassarre notes dryly, they can only take you so far. “Obviously it’s a joke, but it gets at a kernel of truth," he says. "That’s how science works, right? You’ll never completely have all the answers. We may never truly understand what the deal with birds is.” 

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Edible Bird’s Nest: The Functional Values of the Prized Animal-Based Bioproduct From Southeast Asia–A Review

Ting hun lee.

1 School of Chemical and Energy Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, Johor, Malaysia

2 Innovation Centre in Agritechnology for Advanced Bioprocessing, Universiti Teknologi Malaysia, Pagoh Research Center, Johor Darul Takzim, Malaysia

Waseem A. Wani

Chia hau lee, kian kai cheng, sheikh shreaz.

3 Oral Microbiology General Facility Laboratory, Faculty of Dentistry, Health Sciences Center, Kuwait University, Safat, Kuwait

Syieluing Wong

Norfadilah hamdan, nurul alia azmi.

Imma Pagano , University of Salerno, Italy

Edible Bird’s Nest (EBN) is the most prized health delicacy among the Chinese population in the world. Although some scientific characterization and its bioactivities have been studied and researched, no lights have been shed on its actual composition or mechanism. The aim of this review paper is to address the advances of EBN as a therapeutic animal bioproduct, challenges and future perspectives of research involving EBN. The methodology of this review primarily involved a thorough search from the literature undertaken on Web of Science (WoS) using the keyword “edible bird nest”. Other information were obtained from the field/market in Malaysia, one of the largest EBN-producing countries. This article collects and describes the publications related to EBN and its therapeutic with diverse functional values. EBN extracts display anti-aging effects, inhibition of influenza virus infection, alternative traditional medicine in athletes and cancer patients, corneal wound healing effects, stimulation of proliferation of human adipose-derived stem cells, potentiate of mitogenic response, epidermal growth factor-like activities, enhancement of bone strength and dermal thickness, eye care, neuroprotective and antioxidant effects. In-depth literature study based on scientific findings were carried out on EBN and its properties. More importantly, the future direction of EBN in research and development as health-promoting ingredients in food and the potential treatment of certain diseases have been outlined.

Introduction

Edible Bird’s Nest (EBN) is a secretion created by swiftlets. Erodramus (echolocating swiftlets) and Collocalia (non-echolocating swiftlets) are among the two genera of swiftlets known to produce valuable EBN ( Ma and Liu, 2012 ). Swiftlets are insectivorous birds, predominantly inhabited in South East Asia (SEA) and southern part of China ( Aswir and Wan, 2010 ). The world’s largest producer of EBN is Indonesia, which has the largest colony of swiftlets currently, followed by Malaysia. ( Hobbs, 2004 ). Saliva secreted from the pair of sublingual glands of swiftlets are the principal material used in the construction of the EBN. The sublingual glands of swiftlets increase in weight (2.5–160 mg) and reach their maximum secretory activity during nesting and breeding season ( Jamalluddin et al., 2019 ). The male birds make nests by using their secretion to bind with some feathers and vegetation. The resulting material is shaped into nests with simultaneous attachment to the walls of the caves when is habituated in cave environment. In man-made premises, they are attached to the wooden linter ( Lee et al., 2017 ). The nests are graded based on the dry mass, size, color, impurity and amount of feathers via physical appearance.

EBN has been the delicacy food in Traditional Chinese Medicine (TCM) since the Tang Dynasty (618–907 A.D.) ( Marcone, 2005 ). EBN is cooked using double boiling method with rock sugar to make the Chinese cuisine, namely the bird’s nest soup ( Hobbs, 2004 ). It was reported that Hong Kong is the largest importer of EBN globally, followed by the Chinese community from North America. EBN may be regarded as the most expensive animal by-product in the world, costing USD 2,000–10,000 per kilogram for its high nutritional and medicinal therapeutic values ( Babji et al., 2015 ). The key component of EBN are glycoprotein, calcium, sodium, potassium and carbohydrate ( Quek et al., 2018a ). Owing to its esteem as a prized bioproduct in the East of the globe, EBN is also named as the “Caviar of the East” ( Marcone, 2005 ). EBN has also been used as a health tonic in TCM due to its being a multipurpose general health rejuvenation tonic and social symbolic status delicacy during banquet ( Ghassem et al., 2017 ). TCM claimed that EBN can treat malnutrition, improve metabolism rate, boost immune system and rejuvenate the skin complexion ( Bashir et al., 2017 ). Moreover, in the modern research, EBN also exhibits some interesting therapeutic effects, such as anticancer, anti-aging, phlegm-dissolving, cough-suppressing, anti-tuberculosis, voice-improving, curing general debility and asthenia, and hastening recovery from illness and surgery ( Daud et al., 2019a ). There is a great amount of research taking place on the investigation of the hidden nutritive and pharmacological properties of EBN. Some of the reviews were focused on the authentication and identification methods of EBN, its bioactive components and food values ( Lin et al., 2006 ; Wong, 2013 ; Lee et al., 2018 ). However, none of the reviewers have discussed the latest challenges facing by the researchers in EBN research field, such as the important substrates that contribute to the medicinal properties in EBN. Therefore, it is worthwhile to review the advances in the research involving EBN as a functional food from animal-based bioproducts and to discuss or address the challenges and future research perspectives of EBN. This manuscript will be served as a reference for the EBN researchers.

Methodology

Published data from 2000 to 2019 were retrieved from the Web of Science (WoS), in August 2020, by using the following search string: TS = [(edible bird* nest*)]. Only publications in English language that report the functional values of EBN were included for subsequent analysis. The duplicate results were removed from the search. Current EBN trend observed in the Malaysia industry is also included in this review.

The Trend of Edible Bird’s Nest Publications

A thorough search of the literature on WoS indicated that approximately 170 research publications consisting of various types of documents appeared in this topic. Out of 170 articles, only 124 publications were considered in this review which consists 119 original research articles and five review papers. The available publications discussed several aspects related to collection, extraction, purification, authentication, nutritive values, medicinal significance, and other important facts of EBN. According to the search and summarized in Figure 1 , the publications on this topic remained low in 2000–2011. However, in 2012–2019, there is an increase in annual publications, with irregular trend. A noticeable and dramatic increase in publications numbers on this topic occurred since 2012. An increase on the number of citations has revealed the significant attention on the EBN work to the global scientific community.

A pictorial depiction of the steadily growing interest in the research on EBN from 2000 to 2019.

Overview of Edible Bird’s Nests

EBN is the hardened secretion produced by several species of swiftlets originally inhabiting in the limestone caves. EBN weighs at least 1–2 folds of the swiftlet’s body weight and can accommodate only the adult bird and nestlings. The swiftlets take around 35 days to complete the construction of the nest ( Marcone, 2005 ). White nests ( Figure 2A ) are almost entirely made from saliva ( Sims, 2008 ), while black nests ( Figure 2B ) comprised about 45–55% feathers and small dried leaves ( Zulkifli et al., 2019 ). The white nests are mostly produced in the bird premises and only a little amount is found in the caves, whereas the black nests are only harvested in caves. Some slightly or entirely dull orange-red to brownish red nests called Xueyan or Xueyanwo in Chinese are occasionally found in caves and swiftlet houses. Xueyan is a Chinese word with the meaning “blood nest” or the blood-coloured nest which arise from the resemblance in the color of the blood. Red nests or blood nests ( Figure 2C ) are supposed to have higher health benefits and thus, fetch a higher price than white nests in the market ( But et al., 2013 ). The EBN names deserved some special attention also. The first step is to identify them with color, for example, white nest, black nest and also red nest. White and black nests are explained above but the most interesting is the red or blood nests. Blood nest story was invented by the Hong Kong people where it is made to believe that the swiftlets will secrete blood (the best essence) when there is no more saliva to be used to build the nest. This makes the best quality nest ( Lee et al., 2017 ). However, some researchers have suggested that red color might be due to the absorption of the minerals from the wall where the nest was attached ( Wong et al., 2018a ; Shim and Lee, 2018 ). Due to the higher price and hence better profit, some of the EBN processors decided to fake the blood nest with all kinds of dreadful methods. This has resulted in the “sodium nitrite crisis issues” that happened in 2011. China government has banned the import of EBN which caused multimillion dollar losses in Malaysia, after detecting a high content of sodium nitrite in some of the EBN. Subsequently, the Malaysian government has taken the initiative to standardize the EBN names based on the harvested location: the cave and house nest ( Lee et al., 2017 ). It is categorized into only two major types based on the location where the nest is harvested. They totally did not acknowledge the red nest existence simply because there were too many ambiguous points to categorize them. After the ban was lifted in 2014, the content of sodium nitrite was controlled at 30 ppm which followed the Malaysian Food Regulation 1985 and Malaysia Standard MS 2334:2011 ( Quek et al., 2015 ). Till today, Malaysia remains as one of the highest exporters of EBN to China.

An overview of white (A) , black (B) and red (C) EBNs.

Traditional Value and Composition of Edible Bird’s Nest

EBN was once portrayed as a symbol of social status in ancient Chinese society ( Jamalluddin et al., 2019 ) due to its rarity and high price. TCM prescribed EBN as the remedy for consumptive illnesses, tuberculosis , alleviating asthma, dry coughs, haemoptysis, asthenia, improving voice, difficulty in breathing, general weakness of bronchial ailment and relieving gastric troubles ( Ghassem et al., 2017 ). Besides, EBN is traditionally believed to raise libido, fortify the immune system, promote growth, improve concentration, increase energy and metabolism, and regulate circulation ( Bashir et al., 2017 ). Although the efficacy of EBN extracts in maintaining youthfulness and increasing physical strength have yet to be tested, but there is scientific evidence on EBN supplementation indicating that it could improve skin texture and alleviate the aging processes ( Wong, 2013 ; Hwang et al., 2020 ). Based on these studies, EBN consumption may promote the human health.

Protein is the major component in EBN which are commonly used for constructing the cells and tissues and consequently driving to other metabolic functions. Based on the previous studies, the average protein content in EBN is ranging from 50 to 55% of the dried weight ( Wong et al., 2018c ). In addition to the protein contents of EBN, carbohydrates form another major portion of its composition ( Figure 3A ) ( Babji et al., 2018 ). The main carbohydrates present in EBN is sialic acid. Sialic acid facilitates development of gangliosides structure in the brain ( Wang and Brand-Miller, 2003 ). Interestingly, ingestion of it can enhance and improve the neurological and intellectual for infants. Some other main and major ingredients in EBN are the essential trace elements such as calcium, phosphorus, iron, sodium, potassium, iodine and essential amino acids ( Hun et al., 2015 ).

Total composition (A) , amino acid (B) , mineral and metal ions (C) in EBN ( Marcone, 2005 ; Ma and Liu, 2012 ).

Based on these contents, EBN serves as a highly nutritious and health restorative food suitable for consumption by all age groups and genders. The modern analysis of its composition has been reported by many researchers as displayed in Figure 3 . Out of the twenty types of amino acids desired by human, eighteen types of amino acids are detected in EBN. These include nine essential amino acids (phenylalanine, valine, threonine, histidine, tryptophan, isoleucine, methionine, lysine and leucine) required by human body for the growth and reparation of the tissue ( Azmi et al., 2021 ). Out of nine essential amino acids, two of them, namely lysine and tryptophan, are not present in most plant protein. Hence, EBN could provide a complete amino acid for the vegetarians since it is categorized as vegan as it is not meat or animal blood.

Based on the content reported by various researchers, there were some differences in amino acid contents ( Figure 3B ). The actual causes of these differences are not known. However, these variance could be due to the EBN samples that were obtained from different places ( Quek et al., 2018b ). Also, the samples obtained could have been processed and adulterated ( Huang et al., 2018 ). This is due to the fact that researchers could not standardize the EBN processing and cleaning method. Most of the time, samples were just obtained from sponsors or retailers but not knowing the actual process that had been carried out that make the variants.

The minerals and metal ions content ( Figure 3C ) in the EBN were either produced by the swiftlets (who built EBN) or leached from the environment. The content ranges are fairly wide as the samples were from various places and types. The excess mineral present in the food will cause negative effects and jeopardize human health, especially the heavy metal (Lead, Copper, Zinc, Mercury and Cadmium) when entering the human complex body through either inhalation, ingestion, and dermal contact. As described previously, some of these trace minerals and metal ions such as Lead, Mercury, Arsenic and Cadmium could have long term side effects in humans leading to various type of disease even at the small dose of ingestion or exposure ( Zheng et al., 2020 ). Some of the heavy metal content in EBN showed in Figure 3C have alarming excess contents set by the majority food legislations (0–1 ppm). It is suggested that the heavy metal content limit should be enforced as this product is popular among children and more seriously, among pregnant ladies ( Lee et al., 2017 ).

Traditionally, the benefit of EBN consumption in elderly include strengthening of lung and kidney, improving of the spleen, enhancing appetite and phlegm clearances. EBN helps to improve immunity in children, and strengthens the function of the kidney and lung in men ( Quek et al., 2018a ). Based on EBN’s content, in summary, EBN may be termed as a complete food enriched with a huge diversity of proteins, lipids, amino acids, carbohydrates, minerals and vitamins. Some of the essential amino acids, sialic acid, and other key constituents of EBN might have great health benefits in terms of general health especially on lung strengthening, improve skin health and anti-aging ( Wang et al., 2019 ). Some of the recent developed EBN based products are shown in Figure 4 . Till now, there has been little or none of the research on its functional and medicinal properties of EBN. It is further elaborated and discussed in the following section.

Some of the famous EBN market products based on foods labeled, outlook and, food products. (A) Bird’s nest soup, (B) Bird’s nest instant energy drink, (C) Vietnam bird’s nest powder, (D) Brand new concept EBN powder, (E) Bird’s nest drink, (F) Bird’s nest pudding recipe, (G) Instant Malaysian cubilose nourishing tonic and (H) Bird’s nest granules for supplements. The image is adapted from ( Yen, 2015) .

Pre-Clinical Analysis and Therapeutic Effects of Edible Bird’s Nest

The effects of EBN extract have been summarized in Table 1 with details.

Summary of studied effects using EBN extract.

Table 1 Summary of pre-clinical studies on the therapeutic effects of EBN extract.

Antiviral Effects

Viruses are micro infectious agents which can only replicate in living cells of organisms that act as a host. Viruses can infect all living organisms that include plants, animals, bacteria and archaea ( Koonin et al., 2006 ). Most of the viral infections have been reported as leading to lysis of the cell by changing the structure of cell membrane that result to the apoptosis of the host cells ( Haghani et al., 2016 ). The most prevalence disorders due to viral infections are Influenza, Chickenpox, Cold Sores, Avian Influenza, Severe Acute Respiratory Syndrome (SARS) and Acquired Immunodeficiency Syndrome (AIDS).

Flu or influenza is a common viral infection that attacks the human population in the world. People who get infected by the influenza virus may be having varies symptoms like sore throat, muscle pains, running nose, headache, coughing, tired feeling and sometimes may come together with a high fever. Previous study on EBN has shown its potential to treat influenza virus infection in Madin-Darby Canine Kidney Epithelial (MDCK) cells. It also prevents human erythrocytes from undergoing hemagglutination by influenza A viruses ( Haghani et al., 2016 ). Besides, after hydrolyzation with Pancreatin F, EBN extract also has reported the inhibition of the infection in a host range-depended manner with the human, porcine, and avian influenza viruses ( Guo et al., 2006 ). The bioactive compounds such as sialic acid and thymol derivative have given EBN the potential to inhibit the virus. However, Collocalia mucoid or EBN contained a substrate for influenza virus sialidase Saengkrajang et al. (2013) , whereby the inhibition can be disrupted by neuraminidase to some extent. Thus, EBN does not protect against influenza viruses sialidase. On the other hand, there was a report that suggested that the potential of EBN extract as an antivirus agent may be attributed to other inhibitory substances in the EBN that may be work together in a complex and bring the antiviral function in EBN. For instance, there was a previous study showed that N-acetylneuraminic acid may play a role in regulating the antiviral activity in EBN ( Saengkrajang et al., 2013 ).

Interestingly, EBN displays no side effects to the MDCK cells and erythrocytes even at a high concentration of 4 mg/ml. Thus, EBN extract which has undergone Pancreatin F treatment and have a smaller molecular size is highly potential to be used in antiviral treatment due to its effectiveness and safety properties ( Guo et al., 2006 ). Further study was carried out by Yagi et al. (2008) where they presented the N-glycosylation profile of EBN. The authors illustrated a tri-antennary N-glycan with the alpha 2,3-N-acetylneuraminic acid residues as a core component of the EBN. The authors further suggest that the sialylated high-antennary N-glycans are the core components that regulate the inhibition of influenza viral infection.

Overall, there are limited studies that demonstrated the antiviral properties of EBN. Thus, more analyses are needed to investigate the EBN antiviral activity toward the other pathogenic viruses. Although some of the antiviral activity in EBN have been attributed to the presence of N-acetylneuraminic acid and sialylated high-antennary N-glycans, it is important to ascertain other active ingredients in EBN that could possess antiviral properties. It is also vital to establish the active ingredients mechanisms of EBN that showed antiviral effects.

Anticancer Effects

Cancer is one of the most common and lethal diseases after cardiovascular diseases ( Zhao et al., 2016 ). It is a major public health havoc all over the world. Therefore, anticancer agents have always been of great interest ( Ali et al., 2011 ; Saleem et al., 2013 ). Aswir and Wan (2010) documented the effects of EBN on the progression of epithelial colorectal adenocarcinoma cells (Caco-2 cells) in human. The EBN samples used two commercial brands and four unprocessed samples taken from the Department of Wildlife and National Parks, Kuala Lumpur. Analysis was done using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to determine the anticancer properties of the EBN samples. The authors observed that only 84 and 115% cells proliferated upon treatment using EBN samples from the two commercial brands. Nevertheless, the assay using unprocessed EBN samples from North, South and East Coast zones, resulted in 35, 47, and 91% of cell proliferation, respectively. It was reported the variations in the proliferation percentages of Caco-2 cells is subject to the type and source of EBN used ( Aswir and Wan, 2010 ). These preliminary studies suggested that some of the constituents of EBN must be imparting into human body or cancer cells with potential to kill rapidly dividing cancer cells. However, the exact nature and the fate of the components of EBN responsible for the anticancer effects were not detected.

Complementary and Alternative Medicine (CAM) is a branch of medical and health care systems that include treatments and medications that are not regarded to be part of modern medical practices ( Cassileth and Deng, 2004 ). CAM usage is quite popular among cancer patients. In Singapore, patients from western and eastern cultures who seek for cancer treatment were introduced to CAM practices either by taking TCM health supplements, traditional Indian medicine (Ayurvedic) or traditional Malay medicine (Jamu). Lim et al. (2006) documented EBN used in CAM for pediatric oncology patients in Singapore. The main therapeutic ingredients of CAM are alimentary changes, herbal supplement or tea and EBN. The authors suggested that CAM has a broad impact on every aspect of the healthcare system including pediatric oncology. In a similar fashion, Shih et al. (2009) documented the usage of EBN in CAM for adult cancer patients in Singapore. About 403 adult cancer patients who are taking medication at the Ambulatory Treatment Unit of National Cancer Center Singapore have answered a survey form. Based on the questionnaire analyses, 46% claimed taking EBN in their CAM and TCM. As part of the treatment. 54% of the respondents reported the use of EBN during CAM treatment to their oncologist and surprisingly, about 66.4% of the oncologists agreed with the application. Effectiveness from the combination of EBN and CAM to treat cancer is benefited by more than half of the patients. This report shows the advantages of EBN as alternative medicine in improving health of cancer patients.

The studies involving the anticancer evaluation of EBN extracts is yet to be carried out and tested on all range of cancer cells. Based on the literature found, most of the study were very preliminary and it is crucial for the EBN to be screened over a range of cancer cell lines so that a strong justification on its anticancer potential can be documented. Further investigations are needed to elucidate the exact role of different EBN constituents toward cancer cells.

Human Adipose-Derived Stem Cells Proliferation

Stem cells are basic cells which are undifferentiated with a potential to differentiate into many different types of cells. Adipose Stem Cells (ASCs) are generally ubiquitous in all white adipose tissue. The pluripotent ASCs may find differentiation into other types of the mesenchymal cells, such as adipocytes, osteoblasts, chondrocytes and myocytes ( Zuk et al., 2001 ; Zuk et al., 2002 ). Due to the mesodermal origin of adipose cells, their differentiation into neural tissue of ectodermal origin is unlikely ( Tholpady et al., 2006 ). However, in vitro anti-oxidant activity of adipose cells revealed a bipolar morphology which is indistinguishable to neuronal cells ( Boone et al., 2000 ). Stem cells are largely important in the regeneration or repair of aberrant or damaged tissues. ASCs are regarded as the most potent among the mesenchymal stem cells due to its ample confirmations of their pluripotency, multiplying capability and minimum donor morbidity ( Ogawa, 2006 ). Besides, ASCs presence as highly potential agents in regenerative medicine as their cells can be collected in a huge volume with minimum donor-site morbidity. In the last decade, several studies have pointed to the use of ASCs in clinical applications in future. Roh et al. (2012) documented the induction of proliferation of Human Adipose-Derived Stem Cells (hADSCs) by EBN extract. EBN extract was revealed to stimulate the hADSCs cell proliferation via the production of vascular endothelial growth factor (VEGF) and Interleukin 6 (IL-6). The production of VEGF and IL-6 was triggered by the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF- κ B) and activator protein 1 (AP-1). Interestingly, EBN extract also induced the production of VEGF and IL-6. The EBN extract induced production of VEGF and IL-6 was inhibited by PD98059 [a p44/42 mitogen-activated protein kinase (MAPK) inhibitor], SB203580 (a p38 MAPK inhibitor) and ammonium pyrrolidinedithiocarbamate (PDTC; an NF- κ B inhibitor), but not SP600125 [c-Jun N-terminal kinase (JNK) inhibitor]. Similarly, EBN extract-induced proliferation of hADSCs was also limited by PD98059, SB203580, and PDTC but not SP600125. Thus, EBN extract that promoted hADSCs proliferation mainly occurred by amplified IL-6 and VEGF genes that was mediated by the regulation of activation of NF- κ B and AP-1 through p44/42 MAPK and p38 MAPK.

In a nutshell, this report highlighted the potential of EBN extract for the improvement of the self-renewal of hADSCs through the enhancement of growth and multiply capability, which suggested that EBN extract may function as an external element to improve self-renewal by increasing the proliferative capacity of hADSCs. EBN extract affected the proliferation of typical healthy human cells only with no remarkable effects on modified cell lines or mutant cells, which indicated the cell specific effects of EBN extract toward normal cells. However, the details into which the active components of EBN were responsible for these effects still remain to be explored. Therefore, the details of specific component or a group of components of EBN that are responsible for these effects warrant further investigation.

Epidermal Growth Factor-Like Activity

EGF promotes cell growth, dividing and proliferation by joining to the binding site at the epidermal growth factor receptor (EGFR). The size of Human EGF protein is 6,045 Da and it comprises three intramolecular disulfide bonds that linked together with 53 amino acid residues ( Harris et al., 2003 ). EGF binds to the surface of EGFR with high affinity and activates the ligand-induced dimerization ( Dawson et al., 2005 ). The binding will promote the activation of intrinsic protein-tyrosine kinase activity of the receptor. The activation of tyrosine kinase activity induces a signal transduction cascade in several biochemical changes within the cell such as the elevated of intracellular calcium levels, up regulated of the protein synthesis and glycolysis process, and increased of the expression level of the EGFR targeted gene. This leads to DNA synthesis and cell proliferation ( Albishtue et al., 2018 ). Kong et al. (1987) was the first to demonstrate that there is a particular component in the EBN extract that has the EGF-like activity. The EGF-like substance was semi-purified from aqueous extract of the EBN using a Bio-Gel P-10. Following semi-purification, the EGF-like activity of EBN was identified using a series of biochemical analyses such as protein assays that include gel electrophoresis and competitive binding assays. Preliminary study using a specific radioreceptor assay showed the semi-purified EGF-like activity of EBN could generate a competitive binding curve that is parallel to the standard curve. Besides, the EGF-like component present in the EBN extract also could stimulate DNA synthesis by inducing the thymidine inclusion in the quiescent culture of the embryonic fibroblasts (3T3 fibroblasts). Analysis using heat treatment, trypsin digestion and mEGF (EGF isolated from mouse) antibody to investigate the simulation of DNA synthesis in human fibroblasts, the semi-purified EGF-like activity of EBN shown the ability to alter the stimulation of thymidine incorporation with the fibroblasts culture by restricted the trypsin digestion and eventually destroyed the its activity. Consistent results were recorded where the activity of mEGF and EGF-like activity derived from EBN were suppressed when treated with mEGF antibody. This result indicated that the nest EGF shared many similarities with EGF isolated from mouse or shrew in terms of its physical properties.

This section summarised the possible reason of EGF-like substance in the EBN that may contribute to its rejuvenating properties. However, there is a need to find out the possible substance, and characterize its structure through in vitro and in vivo studies, both alone and in EBN as a formulation.

Enhancement of Bone Strength

Bones are rigid structures inside human body that form part of the skeleton system. They are vital to the support system and protect various important organs in the body. Additionally, bones play important roles in the production of white and red blood cells, minerals storage and involve in regulation of body movements and locomotion. Matsukawa et al. (2011) reported the increase of bone strength and dermal thickness of ovariectomized rats after daily consumption of EBN extract. It was reported that the oral consumption of EBN extract improved bone strength of ovariectomized rats due to the increasing of calcium level in the femur of the rats. More importantly, it was also observed the enhancement of dermal thickness following the EBN extract administration. Interestingly, EBN extract did not alter serum estradiol concentration level after EBN extract consumption. Since the ovarian production of estrogen will decline and this will be the major cause of rapid bone loss after menopause Gruber et al. (1984) , Hou et al. (2019) , EBN extract consumption can be an alternative and effective way to increase bone mass and at the same time slow skin aging in postmenopausal women.

Osteoarthritis (OA) is an established degenerative disorder caused by the deterioration of joints that includes the articular cartilage and subchondral bone. It is a painful disorder of the joints often causing stiffness and loss of ability. It is assumed that EBN extract poses some active ingredients that may minimized the occurrence of OA and contribute to the regeneration of cartilage ( Wong et al., 2018b ). In addition, Chua et al. (2013) documented the effects of EBN treatments toward the human articular chondrocytes (HACs) isolated from the knee joint of OA patients. They used hot-water extraction technique to obtain the EBN extract and reported that the supplementation of EBN extract results in increased HACs proliferation. In addition, EBN supplementation down-regulated the expression level of catabolic genes such as matrix metalloproteinases (MMP1 and MMP3), Interleukin 1, 6, and 8 (IL-1, IL-6, and IL-8), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in cultured HACs. In addition, the production of PGE2 was significantly reduced in HACs. However, in anabolic activity analysis, total sulfated glycosaminoglycan production was increased and the expression level of targeted gens such as Aggrecan, type II collagen and SOX-9 were also elevated.

This research report clearly indicated that EBN extract has in vitro chondro-protection effect on HACs. However, it needs to be seen which components of EBN and how they demonstrate such effects. Therefore, EBN may be have a great potential as a replacement nutrient and supplement for osteoarthritis.

Eye Care Effects

Eyes are the main sensory organs of the human body that react to light and give sight. The rod and cone cells in the retina are important conscious sense organs, which can enhance vision and conscious light perception. Our human eye is known to distinguish approximately 10 million colors ( Land and Fernald, 1992 ). The transparent cornea covers three main organs which are pupil, iris, and the anterior chamber. Three distinct cell layers make up the cornea, including the stroma, epithelium and endothelium. Each individual cornea layer has its specialized visual functions. The cell layers also act as protective barriers from external environment ( Lu et al., 2001 ). Approximately 90% of the corneal volume is comprised of the corneal stroma. It has a highly organized extracellular matrix (ECM) and consist of relatively low keratocyte density ( West-Mays and Dwivedi, 2006 ). Keratocytes derived from the corneal layers are mesenchymal-derived cells which directly regulate in the synthesis and secretion of the ECM components ( He and Bazan, 2008 ). Generally, the cornea is damaged by light injuries including localized burns, scraping or abrasions, and some extensive injuries in terms of surface or depth ( Bizrah et al., 2019 ).

There are a few researches performed on the development of medicinal eye care product from EBN. Abidin et al. (2011) studied the effects of EBN on cultured animal corneal keratocytes through the in vitro study, including the isolation of corneal keratocytes with MTT assay in serum contained media (SCM) and serum free media (SFM), morphological observation for detection of phenotypes changes of keratocytes, and determination for gene expression of lumican, collagen type 1 and aldehyde dehydrogenase cells through Reverse Transcription Polymerase Chain Reaction (RT-PCR). Two significant results from Abidin et al. (2011) were reported for better recovery and tissue repair of eye. One significant result was the supplementary effect of EBN from 0.05 to 0.1% showed the highest cell proliferation and the capability to retain phenotypes of corneal keratocytes had been proved by the gene expression and phase-contrast micrographs ( Abidin et al., 2011 ). Another study from Khalid et al. (2019) also clearly indicated that cell proliferation, especially in SCM, was synergistically induced by low EBN concentration. From these literatures, EBN showed great potential to enhance the cell repair from damage through higher cell proliferation rate and proper functioning maintenance in the wound healing of corneal tissues. To develop EBN-based eye drops products before in vivo application, the in vitro test can be a critical first step in the beginning. However, efforts are needed to see if there are any adverse reactions of EBN on other cell types in the vicinity of corneal keratocytes. Besides, it needs to be seen which of the EBN ingredients is responsible for the activity.

Neuroprotective Effects

Neurodegeneration refers to the progressive loss of the structure or function of neurons. Several neurodegenerative diseases such as Parkinson’s (PD), Alzheimer’s (AD) and Huntington’s (HD), occur as eventual results of neurodegenerative processes. PD is an age-related progressive neurodegeneration. It is projected that the prevalence of PD will exceed nine million globally for people who aged more than 50 years old by the end of 2030 ( Szatmari et al., 2019 ). Factors including depletion of dopaminergic neuronal in the substantia nigra and depletion of dopamine in the striatum are the hallmark pathology of PD ( Yew et al., 2018 ). Przedborski (2005) revealed that the abnormal synthesis of α-synuclein (one protein type of presynaptic neuronal) had contributed to the neurodegenerative diseases. The degeneration of motor functions occurs with dopamine depletion and the patients often show clinical symptoms including slow responsiveness, rigidity, and tremor ( Snyder and Adler, 2007 ).

For the past few years, works on EBN and neuroprotective effects have been studied by a number of scientist. For instance, the examination of neuroprotective effect on Human Neuroblastoma SH-SY5Y (HNS) cells using EBN extracts has been reported by Yew et al. (2014) . The study showed that the pancreatin-digested EBN extract was inhibited the cell death of HNS cells up to 75 μg/ml while the maximum non-toxic dose was double (150 μg/ml) for EBN water extract. Nuclear staining and morphological observation indicated that the application of EBN can decrease apoptotic changes induced by 6-hydroxydopamine (6HD) in the HNS cells. Interestingly, cell viability significantly improved with digested EBN extract as compared to the EBN water extract. Nevertheless, EBN water extract showed great roles in the cleavage inhibition of caspase-3, regulate the early apoptotic effect on the phosphatidylserine externalization membrane and neuron recovery with reactive oxygen species build-up. Another similar study also clearly showed that enzyme extraction from EBN might possess neuroprotective effects through the apoptosis inhibition against 6HD-induced degeneration of dopaminergic neurons ( Careena et al., 2018 ). EBN can therefore serve as a viable nutraceutical alternative for the protection against oxidative stress-related neurodegenerative diseases. A different study conducted by Hou et al. (2015) demonstrated the effect of EBN on the toxicity depletion of hydrogen peroxide (H 2 O 2 ) on HNS cells. It was observed that lactoferrin and ovotransferrin within EBN attenuated (H 2 O 2 )-induced toxicity and cytotoxicity. The contents from EBN further decreased ROS with the enhancement of scavenging process which corresponds to a later work done by ( Careena et al., 2018 ) where they found that EBN supplementation inhibited the production of oxidative markers ROS and TBARS in a Wister rat model of LPS-induced neuroinflammation. These reports indicated that EBN may act as a neuroprotective agent against cell oxidative stress and H 2 O 2 -induced cytotoxicity.

Although many researches have been reported on neuroprotective effects of EBN, the current scientific reports have not been able to demonstrate which of the specific EBN components or combination thereof has neuroprotective effects. Hence, the research efforts on EBN are needed to conclude this point in the near future.

Antioxidant Effects

The human body has several anti-oxidant mechanisms that counteract oxidative stress from normal metabolic activity ( Wang et al., 2019 ). The food contains the antioxidants components which are able to fight against the cell-disruptive effects. These antioxidants supplied function either individually or in combination with the endogenous systems. The implications of antioxidants with diet have been shown to be beneficial to human health, but their absence may trigger a number of diseases due to uncontrolled oxidative stress. Numerous vegetables and fruits have been shown to have antioxidant properties against certain cancers and other diseases. Thus, people who regularly rely on fruits and vegetables that are rich in anti-oxidants have lesser frequencies of free radical-induced diseases ( Babji et al., 2018 ). Antioxidants have been the subject of great attention in the present scenario on because of their potential for fighting oxidative stress-related diseases.

EBN has long been first reported to contain antioxidants ( Ghassem et al., 2017 ). As such, the effect of its antioxidants after oral administration is not fully known. EBN’s anti-oxidant properties are attributed to the pool of bioactive compounds such as amino acids, sialic acid, triacylglycerol, vitamins, lactoferrin, fatty acids, minerals, and glucosamine ( Liu et al., 2012 ; Zainab et al., 2013 ; Lee et al., 2020 ). The anti-oxidative effect of EBN showed the presence of two main constituents, namely ovotransferrin and lactoferrin ( Hou et al., 2015 ). The authors also reported their protective effects against H 2 O 2 -induced toxicity on HNS cells. Furthermore, transcriptional changes in anti-oxidant related genes were brought about by lactoferrin, ovotransferrin and EBN were in linked with the neuroprotection ( Hou et al., 2015 ). Yida et al. (2014) documented the in vitro bio-accessibility and antioxidant properties of water extracts of EBN using Oxygen Radical Absorbance Capacity (ORAC) assays and 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay. It was observed that there were low antioxidant activity (about 1% at 1,000 μg/ml) on the undigested EBN water extract for both ABTS and ORAC assays. On the contrary, the digested EBN samples using pepsin, pancreatin and bile extract at similar concentrations showed improved antioxidant activities around 38 and 50% for ABTS and ORAC assays respectively. Besides, the EBN extracts showed non-toxicity toward human hepatocellular carcinoma (HEPG2) cells and protected HEPG2 cells from H 2 O 2 -induced toxicity. In short, enhancement of antioxidant activities of EBN after digestion highlighted some of its functional effects after consumption. However, further analysis such as in vivo studies are needed further characterize the significance of EBN from clinical perspective.

Miscellaneous Effects

There are many therapeutic claims about EBN with no scientific proof which have been handed down from generation to generation. These include claims to treat tuberculosis , dry coughs, asthma, gastric trouble and stomach ulcer ( Jamalluddin et al., 2019 ). Among the Chinese community, it is also renowned for its contribution to the fine porcelain complexion of Chinese beauties. In addition, it is also a normal practice to consume EBN among the Chinese mothers-to-be as a health supplement for both mother and child to have a pair of strong lung and fine complexion ( Babji et al., 2018 ). These legendary claims on the EBN need further research so that the EBN can be developed into traditional medicine with scientific proofs, or at least, a scientifically credited functional food or health supplement. Erectile dysfunction is one of the main male sexual disorders characterized by tenacious inability to keep penile erection enough for pleasing sexual acts ( Ma et al., 2012 ). This disorder mainly occurs due to a continuous spectrum of clinical factors such as difficulties, stress and physical illness in relationship ( Corona and Maggi, 2010 ). Although drugs such as phosphodiesterase-5 inhibitors and testosterone supplication could help to overcome this disorder, the results of these treatments are not always desirable ( Tsertsvadze et al., 2009 ). Ma et al. (2012) studied the effects of EBN on the sexual functioning of castrated rats and found that the seminal vesicle indices and prostate along with the hormone expression of endothelial nitric oxide synthase increased potently in the mouse groups that were treated with EBN. This result indicated that EBN has a potential to be an ideal active ingredient for the development of drugs in treating erectile dysfunction.

Current Challenges and Future Perspectives

Despite the scarcity of science on the therapeutic effects of EBN in the past, several scientific papers have appeared on this subject especially for the past decades. Some of the research papers which have documented and summarized these effects include claim of antiviral, anticancer, proliferation effects on stem cells, epidermal growth factor-like activity, bone strength enhancement, eye care, neuroprotective antioxidant and other health-related effects of EBN. Research needs to be addressed so that the fundamental issues, including the molecular and biochemistry pathway of EBN to alleviate asthma, facilitate renal function, improve complexion, stamina and vitality bone health, could be fully understood. The specific components contributing to a specific function need to be identified. Besides, the correlations between dosages and activities of EBN need to be worked out also. Therefore, it would be a great breakthrough to discover the fundamental mechanisms by which the EBN component exerts both its biological effects in vivo and in vitro studies. Additionally, specific biological functions to specific components of EBN studies and then their isolation and purification component would be valuable. The conclusions and solutions would provide better use of EBN.

From the current literature updates, it can be concluded that EBNs collected from different sources and locations have their differences in composition. Therefore, it would be beneficial to standardize EBN composition and establish a standard operating procedure (SOP) to ensure that a stable and consistent outcome could be obtained. Further investigation focusing on the methodology reported including the complexity and variety of the location sources is needed to justify the variation that exists. If a sample is collected from the market, dealer or a retail shop, it is to be considered as processed since the probability of adulteration is high. One of the most common adulteration is bleaching so that the bird feathers cannot be seen. Others include addition of fortified materials to gain weight such as egg white, jelly, seaweed or even pork skin ( Ma et al., 2019 ). These will definitely deviate the contents of EBN and hence affect the results of experiments.

EBN has long been used as a traditional remedy for some illness but has never been used as a medicine to cure or treat the sickness. This is simply due to the lack of study on the drug development and effective dose of this unique animal-based bioproduct. To the best of our knowledge, there is still no fractionation and isolation of single component work reported for EBN material leading to no specific component to demonstrate its therapeutic. There were only works done for in vitro and in vivo testing using the whole EBN extract with no further characterization on its single compound. Hence, due to insufficient scientific findings and reports, EBN could only regarded as food or at most remedy food.

The rise of allergic issues related to the consumption of EBN have been reported in several health cases. Allergic issues like skin rash, nasal obstruction and facial swelling have been reported in Japan after 5 min of consumption of EBN-contained dessert. The condition of allergic reactions can be in different degree of severity and some severe cases might cause death ( Goh et al., 2000 ). One similar case was reported by National University of Singapore which documented that EBN caused food-induced anaphylaxis among the kids. The anaphylaxis occurrence might be due to the presence of putative allergens and abnormal regulation of Immunoglobulin E mediated process ( Goh et al., 2000 ). Therefore, it becomes critical to identify whether a person is allergic or prone to allergy toward EBN protein by undergoing a skin prick test before consumption. These studies have set the precedence of EBN being an allergen. As the report comes from the highly reputable National University of Singapore, it is of great concern. However, as the test samples were obtained from the market or in other terms, it could have been adulterated by the bird’s premises handler or producer along the way in order to increase profit. The terms “egg white like” protein provides a good clue on this as the EBN processor normally will add egg white on the surface of EBN to provide the good looking luster on EBN to fetch a higher price ( Guo et al., 2018 ). A better understanding and awareness of the consumer market norms and practices would ensure a good sample is applied for research to arrive at a more accurate conclusion.

There are issues arising in relation to the prescription of EBN to cancer patients. Generally, EGF receptors (which had been discussed in Epidermal Growth Factor-Like Activity ) are highly expressed in several tumors cells such as non-small-cell lung, breast, colon, ovarian, renal, head and neck cancers ( Herbst and Shin, 2002 ). Therefore, it may be assumed that EBN consumption might stimulate tumor progression and resist chemotherapy/radiation treatment in tumor cells. However, EBN also promotes healthy cell growth as explained earlier. Cancer patients should not avoid EBN as if it is a taboo merely based on EGF findings alone as EBN has been found to have apoptosis on cancer cells ( Albishtue et al., 2018 ). Nevertheless, these concepts should be researched further to maximize the cancer prevention or treatments.

The discussion in this article proves EBN could be a source of vital health-promoting ingredients with the reported content of amino acids, proteins, carbohydrates, fatty acids and minerals. The discovery of bioactivities in EBN are still in fetal stage and very much unexplored. Overall, the biological effects of EBN are still little explored as the available studies are very much preliminary and have been carried out on limited targets without any emphasis on in vivo studies. Thus, more exploration on the evaluation of bioactivities of EBN are needed to narrow the knowledge gap in EBN research studies. Like of the finding of subject or new material, the primary material should be standardized. The extract based on active ingredients or a standardized operating procedure should be filed. Despite some metabolite profiling studies, there are little information regarding the correlation of the specific active compound of EBN with specific medicinal effect. Furthermore, there is a lack of optimization studies related on the fractionation isolation and purification of active components that attributed to the bioactivities process in EBN. The present era demands further proteomic and genomic research to analyze EBN and its components for humanity’s welfare comprehensively. Finally, research should be encouraged to explore the biological and medicinal properties of EBN. There is a great need to study the correlations between the components and the functions of EBN so that some new and exciting compositions may be discovered. EBN, its extracts and products hold much for future development as possible food and medicinal-based products.

Acknowledgments

The authors express their sincere gratitude to the internal reviewers, LSK and LTK for their unbiased opinion, valuable suggestion and devoted dedication in making this paper a success.

Author Contributions

THL, SW, and NH edited and reviewed the manuscript. KKC and SS conceived and designed the study. WW composed the first draft of the manuscript. CHL and NAA wrote some contents of the manuscript. All authors contributed to the article and approved the submitted version.

This work was supported by the Center of Excellence: Swiftlets Malaysia and Ministry of Science, Technology and Innovation Malaysia (MOSTI) (grant numbers 6371400–10301(H6), 6371400–10301(Q6)).

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

• Abidin F. Z., Hui C. K., Luan N. S., Ramli E. S. M., Hun L. T., Abd Ghafar N. (2011). Effects of Edible Bird's Nest (EBN) on Cultured Rabbit Corneal Keratocytes . BMC Complement. Altern. Med. 11 ( 1 ), 94. 10.1186/1472-6882-11-94 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Albishtue A. A., Yimer N., Zakaria M. Z. A., Haron A. W., Yusoff R., Assi M. A., et al. (2018). Edible Bird’s Nest Impact on Rats’ Uterine Histomorphology, Expressions of Genes of Growth Factors and Proliferating Cell Nuclear Antigen, and Oxidative Stress Level . Vet. World 11 ( 1 ), 71. 10.14202/vetworld.2018.71-79 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Ali I., Wani W. A., Saleem K. (2011). Cancer Scenario in India with Future Perspectives . Cancer Ther. 8 , 56–70. [ Google Scholar ]
• Aswir A. R., Wan N. (2010). Effect of Edible Bird's Nest on Caco-2 Cell Proliferation . J. Food Technol. 8 ( 3 ), 126–130. 10.3923/jftech.2010.126.130 [ CrossRef ] [ Google Scholar ]
• Azmi N. A., Lee T. H., Lee C. H., Hamdan N., Cheng K. K. (2021). Differentiation Unclean and Cleaned Edible Bird's Nest Using Multivariate Analysis of Amino Acid Composition Data . Pertanika J. Sci. Technol. 29 ( 1 ). 10.47836/pjst.29.1.36 [ CrossRef ] [ Google Scholar ]
• Babji A., Etty Syarmila I., Nur'Aliah D., Nurul Nadia M., Hadi Akbar D., Norrakiah A., et al. (2018). Assessment on Bioactive Components of Hydrolysed Edible Bird Nest . Int. Food Res. J. 25 ( 5 ), 1936–1941. [ Google Scholar ]
• Babji A., Nurfatin M., Etty Syarmila I., Masitah M. (2015). Secrets of Edible Bird Nest . Agric. Sci. 1 , 32–37. [ Google Scholar ]
• Bashir M. J., Xian T. M., Shehzad A., Sethupahi S., Choon Aun N., Abu Amr S. (2017). Sequential Treatment for Landfill Leachate by Applying Coagulation-Adsorption Process . Geosystem Eng. 20 ( 1 ), 9–20. 10.1080/12269328.2016.1217798 [ CrossRef ] [ Google Scholar ]
• Bizrah M., Yusuf A., Ahmad S. (2019). An Update on Chemical Eye Burns . Eye 33 ( 9 ), 1362–1377. 10.1038/s41433-019-0456-5 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Boone C., Mourot J., Grégoire F., Remacle C. (2000). The Adipose Conversion Process: Regulation by Extracellular and Intracellular Factors . Reprod. Nutr. Dev. 40 ( 4 ), 325–358. 10.1051/rnd:2000103 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• But P. P.-H., Jiang R.-W., Shaw P.-C. (2013). Edible Bird's Nests—How Do the Red Ones Get Red? . J. Ethnopharmacol. 145 ( 1 ), 378–380. 10.1016/j.jep.2012.10.050 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Careena S., Sani D., Tan S., Lim C., Hassan S., Norhafizah M., et al. (2018). Effect of Edible Bird’s Nest Extract on Lipopolysaccharide-Induced Impairment of Learning and Memory in Wistar Rats . Evid. Based. Complement. Alternat. Med. 7 . 10.1155/2018/93187892018 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Cassileth B. R., Deng G. (2004). Complementary and Alternative Therapies for Cancer . Oncologist 9 ( 1 ), 80–89. 10.1634/theoncologist.9-1-80 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Chua K.-H., Lee T.-H., Nagandran K., Yahaya N. H. M., Lee C.-T., Tjih E. T. T., et al. (2013). Edible Bird’s Nest Extract as a Chondro-Protective Agent for Human Chondrocytes Isolated from Osteoarthritic Knee: In Vitro Study . BMC Complement. Altern. Med. 13 ( 1 ), 19. 10.1186/1472-6882-13-19 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Corona G., Maggi M. (2010). The Role of Testosterone in Erectile Dysfunction . Nat. Rev. Urol. 7 ( 1 ), 46. 10.1038/nrurol.2009.235 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Daud N. A., Mohamad Yusop S., Babji A. S., Lim S. J., Sarbini S. R., Hui Yan T. (2019a). Edible Bird’s Nest: Physicochemical Properties, Production, and Application of Bioactive Extracts and Glycopeptides . Food Rev. Int. , 37 , 1–20. 10.1080/87559129.2019.1696359 [ CrossRef ] [ Google Scholar ]
• Daud N. A., Sarbini S. R., Babji A. S., Yusop S. M., Lim S. J. (2019b). Characterization of Edible Swiftlet’s Nest as a Prebiotic Ingredient Using a Simulated Colon Model . Ann. Microbiol. 69 ( 12 ), 1235–1246. 10.1007/s13213-019-01507-1 [ CrossRef ] [ Google Scholar ]
• Dawson J. P., Berger M. B., Lin C.-C., Schlessinger J., Lemmon M. A., Ferguson K. M. (2005). Epidermal Growth Factor Receptor Dimerization and Activation Require Ligand-Induced Conformational Changes in the Dimer Interface . Mol. Cel Biol. 25 ( 17 ), 7734–7742. 10.1128/MCB.25.17.7734-7742.2005 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Ghassem M., Arihara K., Mohammadi S., Sani N. A., Babji A. S. (2017). Identification of Two Novel Antioxidant Peptides from Edible Bird's Nest ( Aerodramus Fuciphagus ) Protein Hydrolysates . Food Funct. 8 ( 5 ), 2046–2052. 10.1039/C6FO01615D [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Goh D. L., Chew F.-T., Chua K.-Y., Chay O.-M., Lee B.-W. (2000). Edible “Bird's Nest”–Induced Anaphylaxis: An Under-recognized Entity? . J. Pediatr. 137 ( 2 ), 277–279. 10.1067/mpd.2000.107108 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Gruber H. E., Ivey J. L., Baylink D. J., Matthews M., Nelp W. B., Sisom K., et al. (1984). Long-term Calcitonin Therapy in Postmenopausal Osteoporosis . Metabolism 33 ( 4 ), 295–303. 10.1016/0026-0495(84)90187-2 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Guo C.-T., Takahashi T., Bukawa W., Takahashi N., Yagi H., Kato K., et al. (2006). Edible Bird's Nest Extract Inhibits Influenza Virus Infection . Antivir. Res 70 ( 3 ), 140–146. 10.1016/j.antiviral.2006.02.005 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Guo L., Wu Y., Liu M., Ge Y., Chen Y. (2018). Rapid Authentication of Edible Bird's Nest by FTIR Spectroscopy Combined with Chemometrics . J. Sci. Food Agric. 98 ( 8 ), 3057–3065. 10.1002/jsfa.8805 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Haghani A., Mehrbod P., Safi N., Aminuddin N. A., Bahadoran A., Omar A. R., et al. (2016). In vitro and In Vivo Mechanism of Immunomodulatory and Antiviral Activity of Edible Bird's Nest (EBN) against Influenza a Virus (IAV) Infection . J. Ethnopharmacol. 185 , 327–340. 10.1016/j.jep.2016.03.020 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Harris R. C., Chung E., Coffey R. J. (2003). “ EGF Receptor Ligands ,” in The EGF Receptor Family . Editor Carpenter G. (USA: Elsevier; ), 3–14. [ Google Scholar ]
• He J., Bazan H. E. (2008). Epidermal Growth Factor Synergism with TGF-Β1 via PI-3 Kinase Activity in Corneal Keratocyte Differentiation . Invest. Ophthalmol. Vis. Sci. 49 ( 7 ), 2936–2945. 10.1167/iovs.07-0900 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Herbst R. S., Shin D. M. (2002). Monoclonal Antibodies to Target Epidermal Growth Factor Receptor–Positive Tumors: a New Paradigm for Cancer Therapy . Cancer 94 ( 5 ), 1593–1611. 10.1002/cncr.10372 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Hobbs J. J. (2004). Problems in the Harvest of Edible Birds' Nests in Sarawak and Sabah, Malaysian Borneo . Biodivers. Conserv. 13 ( 12 ), 2209–2226. 10.1023/B:BIOC.0000047905.79709.7f [ CrossRef ] [ Google Scholar ]
• Hou Z.-p., Tang S.-y., Ji H.-r., He P.-y., Li Y.-h., Dong X.-l., et al. (2019). Edible Bird’s Nest Attenuates Menopause-Related Bone Degeneration in Rats via Increaing Bone Estrogen-Receptor Expression . Chin. J. Integr. Med. , 27 , 1–6. 10.1007/s11655-019-3209-1 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Hou Z., Imam M. U., Ismail M., Azmi N. H., Ismail N., Ideris A., et al. (2015). Lactoferrin and Ovotransferrin Contribute toward Antioxidative Effects of Edible Bird’s Nest against Hydrogen Peroxide-Induced Oxidative Stress in Human SH-Sy5y Cells . Biosci. Biotechnol. Biochem. 79 ( 10 ), 1570–1578. 10.1080/09168451.2015.1050989 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Huang S., Zhao L., Chen Q., Qin Z., Zhou J., Qiu Y., et al. (2018). Physicochemical Characteristics of Edible Bird’s Nest Proteins and Their Cooking Processing Properties . Int. J. Food Eng. 14 ( 3 ). 10.1515/ijfe-2017-0152 [ CrossRef ] [ Google Scholar ]
• Hun L. T., Wani W. A., Tjih E. T. T., Adnan N. A., Le Ling Y., Aziz R. A. (2015). Investigations into the Physicochemical, Biochemical and Antibacterial Properties of Edible Bird’s Nest . J. Chem. Pharm. Res. 7 ( 7 ), 228–247. [ Google Scholar ]
• Hwang E., Park S. W., Yang J. E. (2020). Anti-aging, Anti-inflammatory, and Wound-Healing Activities of Edible Bird's Nest in Human Skin Keratinocytes and Fibroblasts . Pharmacogn. Mag. 16 ( 69 ), 336. 10.4103/pm.pm_326_19 [ CrossRef ] [ Google Scholar ]
• Jamalluddin N. H., Tukiran N. A., Fadzillah N. A., Fathi S. (2019). Overview of Edible Bird's Nests and Their Contemporary Issues . Food Control 104 , 247–255. 10.1016/j.foodcont.2019.04.042 [ CrossRef ] [ Google Scholar ]
• Khalid S. K. A., Abd Rashed A., Aziz S. A., Ahmad H. (2019). Effects of Sialic Acid from Edible Bird Nest on Cell Viability Associated with Brain Cognitive Performance in Mice . World J. Tradit. Chin. Med. 5 ( 4 ), 214. 10.4103/wjtcm.wjtcm_22_19 [ CrossRef ] [ Google Scholar ]
• Kong Y., Keung W., Yip T., Ko K., Tsao S., Ng M. (1987). Evidence that Epidermal Growth Factor Is Present in Swiftlet's ( Collocalia ) Nest . Comp. Biochem. Physiol. B, Biochem. Mol. Biol. 87 ( 2 ), 221–226. 10.1016/0305-0491(87)90133-7 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Koonin E. V., Senkevich T. G., Dolja V. V. (2006). The Ancient Virus World and Evolution of Cells . Biol. Direct. 1 ( 1 ), 29. 10.1186/1745-6150-1-29 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Land M. F., Fernald R. D. (1992). The Evolution of Eyes . Annu. Rev. Neurosci. 15 ( 1 ), 1–29. 10.1159/000113339 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Lee T. H., Lee C. H., Alia Azmi N., Kavita S., Wong S., Znati M., et al. (2020). Characterization of Polar and Non‐polar Compounds of House Edible Bird's Nest (EBN) from Johor, Malaysia . Chem. Biodivers. 17 ( 1 ), e1900419. 10.1002/cbdv.201900419 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Lee T. H., Wani W. A., Koay Y. S., Kavita S., Tan E. T. T., Shreaz S. (2017). Recent Advances in the Identification and Authentication Methods of Edible Bird's Nest . Food Res. Int. 100 , 14–27. 10.1016/j.foodres.2017.07.036 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Lee T. H., Wong S., Lee C. H., Azmi N. A., Darshini M., Kavita S., et al. (2018). Identification of Malaysia’s Edible Bird’s Nest Geographical Origin Using Gel Electrophoresis Analysis . Chiang Mai Univ. J. Nat. Sci. 19 ( 3 ), 379. [ Google Scholar ]
• Lim J., Wong M., Chan M. Y., Tan A. M., Rajalingam V., Lim L., et al. (2006). Use of Complementary and Alternative Medicine in Paediatric Oncology Patients in Singapore . Ann. Acad. Med. Singap. 35 ( 11 ), 753. [ PubMed ] [ Google Scholar ]
• Lin J., Zhou H., Lai X. (2006). Review of Research on Edible Bird's Nest . J. Chin. Med. Mater. 29 , 85–90. [ Google Scholar ]
• Liu X., Lai X., Zhang S., Huang X., Lan Q., Li Y., et al. (2012). Proteomic Profile of Edible Bird’s Nest Proteins . J. Agric. Food Chem. 60 ( 51 ), 12477–12481. 10.1021/jf303533p [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Lu L., Reinach P. S., Kao W. W.-Y. (2001). Corneal Epithelial Wound Healing . Exp. Biol. Med. 226 ( 7 ), 653–664. 10.1136/bjo.78.5.401 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Ma F.-c., Liu D.-c., Dai M.-x. (2012). The Effects of the Edible Birds Nest on Sexual Function of Male Castrated Rats . Afr. J. Pharm. Pharmacol. 6 ( 41 ), 2875–2879. 10.5897/AJPP12.307 [ CrossRef ] [ Google Scholar ]
• Ma F., Liu D. (2012). Sketch of the Edible Bird's Nest and its Important Bioactivities . Food Res. Int. 48 ( 2 ), 559–567. 10.1016/j.foodres.2012.06.001 [ CrossRef ] [ Google Scholar ]
• Ma X., Zhang J., Liang J., Ma X., Xing R., Han J., et al. (2019). Authentication of Edible Bird’s Nest (EBN) and its Adulterants by Integration of Shotgun Proteomics and Scheduled Multiple Reaction Monitoring (MRM) Based on Tandem Mass Spectrometry . Food Res. Int. 125 , 108639. 10.1016/j.foodres.2019.108639 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Marcone M. F. (2005). Characterization of the Edible Bird’s Nest the “Caviar of the East” . Food Res. Int. 38 ( 10 ), 1125–1134. 10.1016/j.foodres.2005.02.008 [ CrossRef ] [ Google Scholar ]
• Matsukawa N., Matsumoto M., Bukawa W., Chiji H., Nakayama K., Hara H., et al. (2011). Improvement of Bone Strength and Dermal Thickness Due to Dietary Edible Bird’s Nest Extract in Ovariectomized Rats . Biosci. Biotechnol. Biochem. , 75 , 590–592. 10.1271/bbb.100705 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Ogawa R. (2006). The Importance of Adipose-Derived Stem Cells and Vascularized Tissue Regeneration in the Field of Tissue Transplantation . Curr. Stem Cel. Res. Ther. 1 ( 1 ), 13–20. 10.2174/157488806775269043 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Przedborski S. (2005). Pathogenesis of Nigral Cell Death in Parkinson's Disease . Parkinsonism Relat. Disord. 11 , S3–S7. 10.1016/j.parkreldis.2004.10.012 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Quek M. C., Chin N. L., Yusof Y. A., Law C. L., Tan S. W. (2018a). Characterization of Edible Bird's Nest of Different Production, Species and Geographical Origins Using Nutritional Composition, Physicochemical Properties and Antioxidant Activities . Food Res. Int. 109 , 35–43. 10.1016/j.foodres.2018.03.078 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Quek M. C., Chin N. L., Yusof Y. A., Law C. L., Tan S. W. (2018b). Pattern Recognition Analysis on Nutritional Profile and Chemical Composition of Edible Bird’s Nest for its Origin and Authentication . Int. J. Food Prop. 21 ( 1 ), 1680–1696. 10.1080/10942912.2018.1503303 [ CrossRef ] [ Google Scholar ]
• Quek M. C., Chin N. L., Yusof Y. A., Tan S. W., Law C. L. (2015). Preliminary Nitrite, Nitrate and Colour Analysis of Malaysian Edible Bird’s Nest . Inf. Process. Agric. 2 ( 1 ), 1–5. 10.1016/j.inpa.2014.12.002 [ CrossRef ] [ Google Scholar ]
• Roh K.-B., Lee J., Kim Y.-S., Park J., Kim J.-H., Lee J., et al. (2012). Mechanisms of Edible Bird's Nest Extract-Induced Proliferation of Human Adipose-Derived Stem Cells . Evid. Based. Complement. Alternat. Med. , 2012 , 11. 10.1155/2012/797520 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Saengkrajang W., Matan N., Matan N. (2013). Nutritional Composition of the Farmed Edible Bird's Nest ( Collocalia Fuciphaga ) in Thailand . J. Food Compos. Anal. 31 ( 1 ), 41–45. 10.1016/j.jfca.2013.05.001 [ CrossRef ] [ Google Scholar ]
• Saleem K., Wani W. A., Haque A., Milhotra A., Ali I. (2013). Nanodrugs: Magic Bullets in Cancer Chemotherapy . Top. Anti-Cancer. Res. 58 ( 2 ), 437–494. 10.2174/9781608051366113020016 [ CrossRef ] [ Google Scholar ]
• Shih V., Chiang J., Chan A. (2009). Complementary and Alternative Medicine (CAM) Usage in Singaporean Adult Cancer Patients . Ann. Oncol. 20 ( 4 ), 752–757. 10.1093/annonc/mdn659 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Shim E. K.-S., Lee S.-Y. (2018). Nitration of Tyrosine in the Mucin Glycoprotein of Edible Bird’s Nest Changes its Color from White to Red . J. Agric. Food Chem. 66 ( 22 ), 5654–5662. 10.1021/acs.jafc.8b01619 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Sims R. W. (2008). The Identification of Malaysian Species of Swiftlets Collocalia . Ibis 103a ( 2 ), 205–210. 10.1111/j.1474-919X.1961.tb02434.x [ CrossRef ] [ Google Scholar ]
• Snyder C. H., Adler C. H. (2007). The Patient with Parkinson’s Disease: Part I–Treating the Motor Symptoms; Part II–Treating the Nonmotor Symptoms . J. Am. Assoc. Nurse Pract. 19 ( 4 ), 179–197. 10.1111/j.1745-7599.2007.00211.x [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Szatmari S., Ajtay A., Bálint M., Takáts A., Oberfrank F., Bereczki D. (2019). Linking Individual Patient Data to Estimate Incidence and Prevalence of Parkinson’s Disease by Comparing Reports of Neurological Services and Pharmacy Prescription Refills at a Nationwide Level . Front. Neurol. 10 , 640. 10.3389/fneur.2019.00640 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Tholpady S. S., Llull R., Ogle R. C., Rubin J. P., Futrell J. W., Katz A. J. (2006). Adipose Tissue: Stem Cells and beyond . Clin. Plast. Surg. 33 ( 1 ), 55–62. 10.1016/j.cps.2005.08.004 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Tsertsvadze A., Fink H. A., Yazdi F., MacDonald R., Bella A. J., Ansari M. T., et al. (2009). Oral Phosphodiesterase-5 Inhibitors and Hormonal Treatments for Erectile Dysfunction: a Systematic Review and Meta-Analysis . Ann. Intern. Med. 151 ( 9 ), 650–661. 10.7326/0003-4819-151-9-200911030-00150 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wang B., Brand-Miller J. (2003). The Role and Potential of Sialic Acid in Human Nutrition . Eur. J. Clin. Nutr. 57 ( 11 ), 1351–1369. 10.1038/sj.ejcn.1601704 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wang C.-Y., Cheng L.-J., Shen B., Yuan Z.-L., Feng Y.-Q., Lu S.-h. (2019). Antihypertensive and Antioxidant Properties of Sialic Acid, the Major Component of Edible Bird's Nests . Cupr. Top. Nutraceut. R. 17 ( 4 ), 376–380. 10.37290/ctnr2641-452X [ CrossRef ] [ Google Scholar ]
• West-Mays J. A., Dwivedi D. J. (2006). The Keratocyte: Corneal Stromal Cell with Variable Repair Phenotypes . Int. J. Biochem. Cel Biol. 38 ( 10 ), 1625–1631. 10.1016/j.biocel.2006.03.010 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wong R. S. (2013). Edible Bird’s Nest: Food or Medicine? . Chin. J. Integr. Med. 19 ( 9 ), 643–649. 10.1007/s11655-013-1563-y [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wong Z. C., Chan G. K., Dong T. T., Tsim K. W. (2018a). Origin of Red Color in Edible Bird’s Nests Directed by the Binding of Fe Ions to Acidic Mammalian Chitinase-like Protein . J. Agric. Food Chem. 66 ( 22 ), 5644–5653. 10.1021/acs.jafc.8b01500 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wong Z. C., Chan G. K., Wu K. Q., Poon K. K., Chen Y., Dong T. T., et al. (2018b). Complete Digestion of Edible Bird's Nest Releases Free N-Acetylneuraminic Acid and Small Peptides: an Efficient Method to Improve Functional Properties . Food Funct. 9 ( 10 ), 5139–5149. 10.1039/C8FO00991K [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wong Z. C., Chan G. K., Wu L., Lam H. H., Yao P., Dong T. T., et al. (2018c). A Comprehensive Proteomics Study on Edible Bird’s Nest Using New Monoclonal Antibody Approach and Application in Quality Control . J. Food Compos. Anal. 66 , 145–151. 10.1016/j.jfca.2017.12.014 [ CrossRef ] [ Google Scholar ]
• Yagi H., Yasukawa N., Yu S.-Y., Guo C.-T., Takahashi N., Takahashi T., et al. (2008). The Expression of Sialylated High-Antennary N-Glycans in Edible Bird’s Nest . Carbohydr. Res. 343 ( 8 ), 1373–1377. 10.1016/j.carres.2008.03.031 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Yen S. (2015). Edible Bird's Nest. Vietnam . Available at: http://songyen.com/en/edible-birds-nest.html . (Accessed 2020)
• Yew M. Y., Koh R. Y., Chye S. M., Othman I., Ng K. Y. (2014). Edible Bird’s Nest Ameliorates Oxidative Stress-Induced Apoptosis in SH-Sy5y Human Neuroblastoma Cells . BMC Complement. Altern. Med. 14 ( 1 ), 1–12. 10.1186/1472-6882-14-391 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Yew M. Y., Koh R. Y., Chye S. M., Othman I., Soga T., Parhar I., et al. (2018). Edible Bird’s Nest Improves Motor Behavior and Protects Dopaminergic Neuron against Oxidative and Nitrosative Stress in Parkinson’s Disease Mouse Model . J. Funct. Foods 48 , 576–585. 10.1016/j.jff.2018.07.058 [ CrossRef ] [ Google Scholar ]
• Yida Z., Imam M. U., Ismail M. (2014). In vitro bioaccessibility and Antioxidant Properties of Edible Bird’s Nest Following Simulated Human Gastro-Intestinal Digestion . BMC Complement. Altern. Med. 14 ( 1 ), 468. 10.1186/1472-6882-14-468 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Zainab H., Nur Hulwani I., Jeyaraman S., Kamarudin H., Othman H., Lee B. B. (2013). Nutritional Properties of Edible Bird Nest . J. Asian Sci. Res. 3 ( 6 ), 600. [ Google Scholar ]
• Zhao R., Li G., Kong X.-j., Huang X.-y., Li W., Zeng Y.-y., et al. (2016). The Improvement Effects of Edible Bird’s Nest on Proliferation and Activation of B Lymphocyte and its Antagonistic Effects on Immunosuppression Induced by Cyclophosphamide . Drug Des. Devel. Ther. 10 , 371. 10.2147/DDDT.S88193 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Zheng S., Wang Q., Yuan Y., Sun W. (2020). Human Health Risk Assessment of Heavy Metals in Soil and Food Crops in the Pearl River Delta Urban Agglomeration of China . Food Chem. 316 , 126213. 10.1016/j.foodchem.2020.126213 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Zuk P. A., Zhu M., Ashjian P., De Ugarte D. A., Huang J. I., Mizuno H., et al. (2002). Human Adipose Tissue Is a Source of Multipotent Stem Cells . Mol. Biol. Cel. 13 ( 12 ), 4279–4295. 10.1091/mbc.e02-02-0105 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Zuk P. A., Zhu M., Mizuno H., Huang J., Futrell J. W., Katz A. J., et al. (2001). Multilineage Cells from Human Adipose Tissue: Implications for Cell-Based Therapies . Tissue Eng. 7 ( 2 ), 211–228. 10.1089/107632701300062859 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Zulkifli D. A., Mansor R., Md Ajat M. M., Abas F., Ideris A., Abu J. (2019). Differentiation of Malaysian Farmed and Commercialised Edible Bird's Nests through Nutritional Composition Analysis . Pertanika J. Tro. Agric. Sc. 42 ( 3 ), 871–881. [ Google Scholar ]

Bird Flu Is Infecting More Mammals. What Does That Mean for Us?

H5N1, an avian flu virus, has killed tens of thousands of marine mammals, and infiltrated American livestock for the first time. Scientists are working quickly to assess how it is evolving and how much of a risk it poses to humans.

Checking a dead otter for bird flu infection last year on Chepeconde Beach in Peru. Credit... Sebastian Castaneda/Reuters

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By Apoorva Mandavilli and Emily Anthes

Apoorva Mandavilli first reported on bird flu in 2003. Emily Anthes has been writing about bird flu in wild animals since 2022.

• Published April 22, 2024 Updated April 24, 2024

In her three decades of working with elephant seals, Dr. Marcela Uhart had never seen anything like the scene on the beaches of Argentina’s Valdés Peninsula last October.

It was peak breeding season; the beach should have been teeming with harems of fertile females and enormous males battling one another for dominance. Instead, it was “just carcass upon carcass upon carcass,” recalled Dr. Uhart, who directs the Latin American wildlife health program at the University of California, Davis.

H5N1, one of the many viruses that cause bird flu, had already killed at least 24,000 South American sea lions along the continent’s coasts in less than a year. Now it had come for elephant seals.

Pups of all ages, from newborns to the fully weaned, lay dead or dying at the high-tide line. Sick pups lay listless, foam oozing from their mouths and noses.

Dr. Uhart called it “an image from hell.”

In the weeks that followed, she and a colleague — protected head to toe with gloves, gowns and masks, and periodically dousing themselves with bleach — carefully documented the devastation. Team members stood atop the nearby cliffs, assessing the toll with drones.

What they found was staggering: The virus had killed an estimated 17,400 seal pups , more than 95 percent of the colony’s young animals.

The catastrophe was the latest in a bird flu epidemic that has whipped around the world since 2020, prompting authorities on multiple continents to kill poultry and other birds by the millions. In the United States alone, more than 90 million birds have been culled in a futile attempt to deter the virus.

There has been no stopping H5N1. Avian flu viruses tend to be picky about their hosts, typically sticking to one kind of wild bird. But this one has rapidly infiltrated an astonishingly wide array of birds and animals, from squirrels and skunks to bottlenose dolphins, polar bears and, most recently, dairy cows.

“In my flu career, we have not seen a virus that expands its host range quite like this,” said Troy Sutton, a virologist who studies avian and human influenza viruses at Penn State University.

Newfoundland

St. John’s

South Carolina

St. Lawrence

Maine coast

Falkland Islands

South Georgia

Dec. 2021 The H5N1 bird flu virus is detected on a farm in St. John’s, Newfoundland, and in a sick wild gull nearby. Hundreds of birds on the farm died, and the rest were culled. It is the first detection of the virus in North America.

Migrating shorebirds may have carried the virus from Europe to Newfoundland through Iceland or Greenland. Or seabirds that congregate in the north Atlantic Ocean might have carried the virus ashore when they returned to Newfoundland to breed.

Jan. 2022 The virus is first detected in the United States, in wild birds in North and South Carolina.

Summer 2022 Hundreds of harbor seals and gray seals die along the coast of Maine and along the St. Lawrence Estuary in Quebec. The seals may have been infected by living near or eating sick and dead birds.

Fall 2022 After months moving west across the United States and Canada, the virus spreads south into Mexico and Colombia , most likely by migrating birds carrying it down the Pacific Flyway.

Nov. 2022 The virus reaches Peru, causes a mass die-off of pelicans along the coast, and begins to spread to other birds and marine mammals. Confirmed samples are shown as dots.

Early 2023 Thousands of sea lions die in Peru and Chile, the earliest known mass sea lion deaths from the virus. The virus continues spreading down the Chilean coast towards Cape Horn.

Late 2023 The virus rounds Cape Horn and moves north into Argentina and Uruguay, killing sea lions and seals and eventually reaching southern Brazil.

Oct. 2023 The virus also spreads south , entering the Antarctic region for the first time. Birds on the island of South Georgia are infected, followed in January by elephant seals and fur seals . Seabirds on the Falklands Islands are also infected.

The blow to sea mammals, and to dairy and poultry industries, is worrying enough. But a bigger concern, experts said, is what these developments portend: The virus is adapting to mammals, edging closer to spreading among people.

A human pandemic is by no means inevitable. So far at least, the changes in the virus do not signal that H5N1 can cause a pandemic, Dr. Sutton said.

Still, he said, “We really don’t know how to interpret this or what it means.”

Marine mortalities

A highly pathogenic strain of H5N1 was identified in 1996 in domestic waterfowl in China. The next year, 18 people in Hong Kong became infected with the virus, and six died. The virus then went silent, but it resurfaced in Hong Kong in 2003. Since then, it has caused dozens of outbreaks in poultry and affected more than 800 people who were in close contact with the birds.

All the while, it continued to evolve.

The version of H5N1 currently racing across the world emerged in Europe in 2020 and spread quickly to Africa and Asia. It killed scores of farmed birds, but unlike its predecessors it also spread widely among wild birds and into many other animals.

Most infections of mammals were probably “dead-end” cases: a fox, perhaps, that ate an infected bird and died without passing on the virus. But a few larger outbreaks suggested that H5N1 was capable of more.

The first clue came in the summer of 2022, when the virus killed hundreds of seals in New England and Quebec . A few months later, it infiltrated a mink farm in Spain .

In the mink, at least, the most likely explanation was that H5N1 had adapted to spread among the animals. The scale of the outbreaks in sea mammals in South America underscored that probability.

“Even intuitively, I would think that mammal-to-mammal transmission is very likely,” said Malik Peiris, a virologist and expert in bird flu at the University of Hong Kong.

After it was first detected in South America, in birds in Colombia in October 2022, the virus swept down the Pacific coast to Tierra del Fuego, the southernmost tip of the continent, and up the Atlantic coast.

Along the way, it killed hundreds of thousands of seabirds, and tens of thousands of sea lions, in Peru , Chile , Argentina, Uruguay and Brazil. The sea lions behaved erratically, experiencing convulsions and paralysis; pregnant females miscarried their fetuses .

“What happened when the virus moved to South America we had never seen before,” Dr. Uhart said.

Exactly how and when the virus jumped to marine mammals is unclear, but the sea lions most likely came into close contact with infected birds or contaminated droppings. (Although fish make up the bulk of sea lions’ diet, they do sometimes eat birds.)

At some point, it’s likely the virus evolved to spread directly among the marine mammals: In Argentina, the sea lion deaths did not coincide with the mass mortality of wild birds.

“This could suggest that the infection source was not the infected birds,” said Dr. Pablo Plaza, a wildlife veterinarian at the National University of Comahue and National Scientific and Technical Research Council in Argentina.

It is not hard to imagine how the virus might disperse in these animals: Elephant seals and sea lions both breed in colonies, crowding together on beaches where they fight, mate and bark at one another. Elephant seals sneeze all day, dispersing large droplets of mucus each time they do.

It is difficult to prove exactly how and when the virus moved from one species to another. But genetic analysis supports the theory the marine mammals acquired their infections from one another, not birds. Samples of virus isolated from sea lions in Peru and Chile and from the elephant seals in Argentina all share about 15 mutations not seen in the birds; the same mutations were also present in a Chilean man who was infected last year.

There are numerous opportunities for H5N1 to jump from sea mammals into people. One sick male elephant seal that sat for a day and a half on a public beach in Argentina turned out to carry enormous amounts of virus. In Peru, scientists collected samples from sea lion carcasses that lay alongside families enjoying a beach day.

Scavenging animals, such as dogs, could also pick up the virus from an infected carcass and then spread it more broadly: “None of the wildlife exists in their little silos,” said Wendy Puryear, a virologist at Tufts University who studied the New England seal outbreaks.

In some South American countries, apart from a few carcasses that were buried, the rest have remained on the beaches, rotting and scavenged upon.

“How do you even scale up to remove 17,000 dead bodies out in the middle of nowhere, places where you can’t even bring down machinery, and humongous cliffs?” Dr. Uhart said.

A mutating pathogen

Flu viruses are adept at picking up new mutations; when two types of flu virus infect the same animal, they can shuffle their genetic material and generate new versions.

It is unclear exactly how, and how much, the H5N1 virus has changed since it first emerged. One study last year showed that after the virus entered the United States, it quickly mixed with other flu viruses circulating here and morphed into various versions — some mild, others causing severe neurological symptoms.

“So now after 20 years of reassortment, you have a virus that actually does extraordinary well in a whole variety of avian and mammal species,” said Vincent Munster, a virologist at the National Institute of Allergy and Infectious Diseases who has studied the mutations needed for H5N1 to adapt to people.

Every new species that harbors the virus creates opportunities for H5N1 to continue to evolve, and to jump into people.

And the virus may stumble across mutations that no one has yet considered, allowing it to breach the species barrier. That is what happened in the 2009 swine flu outbreak.

That virus did not have the mutations thought to be needed to infect people easily. Instead, “it had these other mutations that no one knew about or thought about before then,” said Louise Moncla, an evolutionary biologist who studies avian influenza at the University of Pennsylvania.

Still, even if the virus jumps to people, “we may not see the level of mortality that we’re really concerned about,” said Seema Lakdawala, a virologist at Emory University. “Preexisting immunity to seasonal flu strains will provide some protection from severe disease.”

What happens next

The U.S. is prepared for an influenza pandemic, with some stockpiled vaccines and antivirals, but its efforts at monitoring the virus may not pick it up quickly enough to deploy those tools.

It took several weeks before farmers, and then officials, knew that H5N1 was circulating in dairy cows.

The dairy farm outbreak has resulted in only one mild human infection, but farms are fertile ground for the virus to jump species — from cat to cow to pig and human, in any order.

Many scientists worry in particular about pigs, which are susceptible to both human and avian flu strains, providing the perfect mixing bowl for viruses to swap genes. Pigs are slaughtered when very young, and newer generations, with no prior exposure to flu, are particularly vulnerable to infections.

So far, H5N1 does not seem adept at infecting pigs, but that could change as it acquires new mutations.

“I never let my kids go to a state fair or animal farm, I’m one of those parents,” Dr. Lakdawala said. “And it’s mostly because I know that the number of interactions that we increase with animals, the more opportunities there are.”

Should H5N1 adapt to people, federal officials will need to work together and with their international counterparts. Nationalism, competition and bureaucracy can all slow down the exchange of information that is crucial in a developing outbreak.

In some ways, the current spread among dairy cows is an opportunity to practice the drill, said Rick Bright, the chief executive of Bright Global Health, a consulting company that focuses on improving responses to public health emergencies. But the U.S. Agriculture Department has been too limited in its approach to testing cows, and has not been as timely and transparent with its findings as it should have been, he said.

On Wednesday, the department ordered that dairy cows moving across state lines to be tested for influenza.

Dr. Rosemary Sifford, the department’s chief veterinarian, said the staff there were working hard to share information as quickly as they can. “This is considered an emerging disease,” she said.

Government leaders are typically cautious, wanting to see more data. But “given the rapid speed at which this can spread and the devastating illness that it can cause if our leaders are hesitant and don’t pull the right triggers at the right time, we will be caught flat-footed once again,” Dr. Bright said.

“If we don’t give it the panic but we give it the respect and due diligence,” he added, alluding to the virus, “I believe we can manage it.”

Apoorva Mandavilli is a reporter focused on science and global health. She was a part of the team that won the 2021 Pulitzer Prize for Public Service for coverage of the pandemic. More about Apoorva Mandavilli

Emily Anthes is a science reporter, writing primarily about animal health and science. She also covered the coronavirus pandemic. More about Emily Anthes

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H5N1 bird flu: What threat does it pose?

Dr. Rajesh Gulati at UC Riverside answers some common questions about the virus and its spread

The World Health Organization has raised concerns about the spread of H5N1 bird flu , the disease caused by infection with avian (bird) influenza (flu) Type A viruses. Currently, H5N1 bird flu is causing outbreaks in U.S. poultry and dairy cows.

Dr. Rajesh Gulati , interim chair of internal medicine at the University of California, Riverside  School of Medicine , answers some questions about H5N1 bird flu. Gulati is the associate dean of graduate medical education at UCR and a practicing hospitalist at Riverside Community Hospital.

Q: How is this new virus strain behaving differently than strains in earlier outbreaks?

This new strain of avian influenza (H5N1) is different from earlier strains because it has adapted and changed. It has used new genetic material from wild bird genes and infected more wild bird species than previous strains have. It has also been affecting mammals — wild ones, such as bears and foxes, but also domesticated ones, like dairy cattle and cats. We can see this new virus strain is also sticking around longer than previous outbreaks. 

Q: How does the virus spread? How might it spread to humans?

The virus initially caused outbreaks in North American poultry species but has now been detected in many types of mammals as well as a few humans. It is spread through droplets or dust from infected animals, which a human can inhale or transfer from hands to the eyes/nose/mouth. We are not sure about the spread from person to person, but viruses are able to adapt and mutate rapidly. It is important to refer to the Center for Disease Control and Prevention for their research and recommendations.

Q: What precautions should people take?

Many precautions need to be taken by those in the dairy industry in direct contact with possibly infected animals, or those who often interact with wild birds. These individuals should be using PPE (such as respirators), creating isolated areas, and monitoring exposures. The virus is affecting dairy cattle; we want to make sure we are not consuming raw milk products, which contain many more dangerous microbes than possibly just H5N1 and are only drinking pasteurized milk. 

In addition, for those of us with pet cats or dogs, it’s important to limit their interactions with wild birds to avoid any spread of the virus to our homes. We should also try to limit our interactions with wild birds, including their feathers, feces, or nests.  

In general, one of the best ways to protect against viruses is frequent hand washing with soap and water and to avoid touching your hands to your face/mouth/nose/eyes if they are contaminated in any way. 

Q: How can the spread be contained?

The current methods of control for H5N1 will likely be quarantining and culling (selective slaughter) of infected animals. If infection is suspected, it’s important to trace it back to the source and see the interactions along the way. If there is a need for a vaccine, COVID has shown us that our research centers can get them made (relatively) quickly and administered to prevent an outbreak from becoming catastrophic. For now, the virus appears to be contained to some domesticated mammals and the individuals who were interacting with them on a frequent basis. 

Q: The virus has jumped to livestock and wild animals. How might this pose a danger to humans?

The lives of humans and the animals we consume and acquire products from are tightly linked. We interact frequently with domestic animals for farming, trade, and food production, which increases the opportunity for zoonotic transmission — infections that are spread between people and animals. It has the possibility of seriously disrupting our food supply and leading to significant economic losses. 

Due to the rapid mutation, this virus can spread across species. It can lead to strains that are more virulent, that is, extremely severe or harmful, or even adapt itself to person-to-person transmission. This could lead to widespread outbreaks or even a global pandemic.  

Header image credit: wildpixel/iStock/Getty Images Plus.

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Engineering student studying flight physics of birds

Sameer pokhrel is working towards advancement in unmanned aerial vehicles.

After earning a bachelor's degree in mechanical engineering in Nepal, Sameer Pokhrel came to the United States to further his education. From an early age, he had a lifelong fascination with aviation. As an adult, he transformed this fascination into a career, pursuing a doctoral degree in aerospace engineering at the University of Cincinnati's historic program. Here, he has succeeded in research, instruction, and was named Graduate Student Engineer of the Month by the College of Engineering and Applied Science.

Why did you choose UC? What drew you here?

Sameer Pokhrel is a doctoral candidate in aerospace engineering at the University of Cincinnati. Photo/provided

I chose the University of Cincinnati primarily because of its strong reputation in aerospace engineering and research.

From an early age, I was fascinated by airplanes and rockets. UC's esteemed reputation in the field of aerospace engineering made me feel like it was the perfect place for my graduate studies. Even though I didn't have the opportunity to visit campus before applying, hearing positive feedback about the university's facilities, resources, and faculty helped my decision.

UC offers the ideal environment for me to grow academically and is preparing me to thrive in my field. I'm glad I chose to be a Bearcat!

Why did you choose your field of study?

When I was young, I would often go plane spotting whenever possible. I remember I used to get very excited when I saw space exploration documentaries on TV.

Later, I realized I could turn this fascination into a career, so I chose mechanical engineering for my undergraduate degree. As aerospace engineering was not directly available at the time in Nepal, I chose it as my minor.

After completing my undergraduate studies, I worked as a design engineer on a fixed wing Unmanned Aerial Vehicle (UAV) for medical delivery in the hilly region of Nepal. There, I realized my interest in dynamics and control, which led me to pursue a graduate degree in aerospace engineering, focusing on dynamics and control. 

Describe your research work. Why does it inspire you?

In my research, I focus on studying the application of unconventional control techniques in bio-inspired systems of UAVs. My work can be divided into two main parts: theoretical developments and applications. On the theoretical front, I work nonlinear control techniques, particularly Extremum Seeking Control, which is a model-free, adaptive control technique. I aim to develop tools to better analyze and improve the structures of such control systems for real-life applications. On the application front, I explore the flight physics of soaring birds, which fly long distances without flapping their wings. I investigate whether we can mimic the optimized flight of these birds in UAVs by examining the relationship between extremum seeking control and their flight patterns. 

What inspires me most about this research is the opportunity to push the boundaries of current literature and bridge the gap between theory and practice.

I'm driven by the prospect of developing novel control techniques that are versatile and less dependent on specific models. Furthermore, if we can replicate the dynamic soaring flight maneuver of birds, it could lead to substantial technological advancements in UAVs. Imagine the possibility of flying UAVs for hundreds of kilometers like soaring birds.

This perspective is truly miraculous and motivates me to continue exploring and innovating in this field. 

What are a few accomplishments of which you are most proud?

Academically, I'm proud to have published my research work in prestigious journals such as the SIAM Journal on Applied Mathematics, the International Journal of Control, Automation and Systems, and Bioinspiration and Biomimetics.

I believe these publications have not only validated my research efforts but have also contributed to the academic community. Moreover, presenting my research at conferences like the American Institute of Aeronautics and Astronautics SciTech, the Society for Industrial and Applied Mathematics (SIAM) Conference of Control and its Applications, and the SIAM Conference on Life Science was immensely beneficial. 

These experiences allowed me to share my work with peers and experts while simultaneously providing me with valuable learning and networking opportunities.

Additionally, participating in events like the Graduate Student Mathematical Modeling Camp and the Mathematical Problems in Industry Workshop 2023 helped me experience practical industry problems. The time I spent with bright minds during the brainstorming sessions is something I will never forget.

Also, I'd like to give a huge shoutout to the UC Piloting Club for providing me with a real flying experience by putting me in the co-pilot seat of a real airplane. All of these experiences have been instrumental and impactful in shaping my academic and personal journey during my time at the university. 

When do you expect to graduate? Do you have any other activities you'd like to share?

I expect to graduate in the summer of 2024 and hope to get experience in industry before returning to academia. I also love to travel and experience new things. Traveling provides the necessary break between projects and reenergizes me for my upcoming work. I also love watching and playing sports, especially soccer, which I play on a regular basis. 

Want to learn more?

Explore graduate programs at the College of Engineering and Applied Science. 

Featured image at top: UAV flying. Photo/pixabay

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