Chicken#Domestication

Terms for chickens include:

• Biddy: a chicken, or a newly hatched chicken{{cite web |url=https://www.dictionary.com/browse/biddy |title=Definition of biddy |publisher=Dictionary.com |access-date=May 7, 2021 |archive-date=May 7, 2021 |archive-url=https://web.archive.org/web/20210507151125/https://www.dictionary.com/browse/biddy |url-status=live}}{{cite web |url=https://www.collinsdictionary.com/us/dictionary/english/biddy |title=Biddy definition and meaning |publisher=Collins English Dictionary|access-date=May 7, 2021 |archive-date=May 7, 2021 |archive-url=https://web.archive.org/web/20210507010137/https://www.collinsdictionary.com/us/dictionary/english/biddy |url-status=live}}
• Capon: a castrated or neutered male chicken{{efn|The surgical and chemical castration of chickens is now illegal in some parts of the world.}}
• Chick: a young chicken{{cite web |title=Chick |url=https://dictionary.cambridge.org/us/dictionary/english/chick |url-status=live |publisher=Cambridge Dictionary |archive-url=https://web.archive.org/web/20150907132725/http://dictionary.cambridge.org/us/dictionary/english/chick |archive-date=September 7, 2015 }}
• Chook {{IPAc-en|tʃ|ʊ|k}}: a chicken (Australia/New Zealand, informal){{cite web |title=Chook |url=https://dictionary.cambridge.org/us/dictionary/english/chook |url-status=live |access-date=March 4, 2021 |website=Cambridge Dictionary |archive-url=https://web.archive.org/web/20150907151220/http://dictionary.cambridge.org/us/dictionary/english/chook |archive-date=September 7, 2015 }}
• Cock: a fertile adult male chicken{{cite web |title=Cock |url=https://dictionary.cambridge.org/us/dictionary/english/cock |url-status=live |access-date=March 4, 2021 |publisher=Cambridge Dictionary |archive-url=https://web.archive.org/web/20150907102240/http://dictionary.cambridge.org/us/dictionary/english/cock |archive-date=September 7, 2015 }}{{Cite web |title=Hen |url=https://dictionary.cambridge.org/us/dictionary/english/cock |url-status=live |access-date=March 4, 2021 |publisher=Cambridge Dictionary |archive-url=https://web.archive.org/web/20150907102240/http://dictionary.cambridge.org/us/dictionary/english/cock |archive-date=September 7, 2015 }}
• Cockerel: a young male chicken{{cite encyclopedia |url=http://dictionary.reference.com/browse/cockerel |title=Cockerel |publisher=Dictionary Reference |access-date=August 29, 2010 |archive-url=https://web.archive.org/web/20160307191527/http://dictionary.reference.com/browse/cockerel |archive-date=March 7, 2016 |url-status=live }}
• Hen: an adult female chicken{{cite web |title=Hen noun |url=https://www.merriam-webster.com/dictionary/hen |publisher=Merriam-Webster |access-date=February 2, 2024}}
• Pullet: a young female chicken less than a year old.{{cite encyclopedia |url=http://dictionary.reference.com/browse/pullet |title=Pullet |publisher=Dictionary Reference |access-date=August 29, 2010 |archive-url=https://web.archive.org/web/20101109014624/http://dictionary.reference.com/browse/pullet |archive-date=November 9, 2010 |url-status=live }} In the poultry industry, a pullet is a sexually immature chicken less than 22 weeks of age.{{Cite web |title=Overview of the Poultry Industry |url=https://dese.mo.gov/sites/default/files/aged%20-PoultrySR.pdf |url-status=live |publisher=Missouri Department of Elementary and Secondary Education |page=8 |archive-url=https://web.archive.org/web/20201023230530/https://dese.mo.gov/sites/default/files/aged%20-PoultrySR.pdf |archive-date=October 23, 2020 }}
• Rooster: a fertile adult male chicken, especially in North America. Originated in the 18th century, possibly as a euphemism to avoid the sexual connotation of the word cock.{{Cite web |title=Definition of Rooster |url=https://www.merriam-webster.com/dictionary/rooster |publisher=Merriam-Webster |access-date=March 6, 2021 |archive-date=April 22, 2021 |archive-url=https://web.archive.org/web/20210422030634/https://www.merriam-webster.com/dictionary/rooster |url-status=live}}[http://www.americanheritage.com/content/why-do-we-say-17 Hugh Rawson] {{Webarchive |url=https://web.archive.org/web/20170701144833/http://www.americanheritage.com/content/why-do-we-say-17 |date=July 1, 2017 }} "Why Do We Say...? Rooster", American Heritage, August–September 2006.[https://www.etymonline.com/search?q=rooster Online Etymology Dictionary] {{Webarchive |url=https://web.archive.org/web/20201111222713/https://www.etymonline.com/search?q=rooster |date=November 11, 2020 }} Entry for rooster (n.), May 2019
• Yardbird: a chicken (southern United States, dialectal){{cite book |last=Berhardt |first=Clyde E. B. |title=I Remember: Eighty Years of Black Entertainment, Big Bands |year=1986 |publisher=University of Pennsylvania Press |isbn=978-0-8122-8018-0 |oclc=12805260 |page=153}}

Chicken can mean a chick, and this was historically the meaning of the word chicken,{{Cite web |date=December 2024 |title=chicken (n.) |url=https://doi.org/10.1093/OED/2784909248 |access-date=February 14, 2025 |website=Oxford English Dictionary|doi=10.1093/OED/2784909248 }} as in William Shakespeare's play Macbeth, where Macduff laments the death of "all my pretty chickens and their dam".Shakespeare, William, Macbeth, Act 4 Scene 3, lines 217–229. The usage is preserved in placenames such as the Hen and Chicken Islands.{{Cite web |title=Chicken |url=https://www.merriam-webster.com/dictionary/chicken |url-status=live |access-date=March 4, 2021 |website=Merriam Webster Dictionary |archive-url=https://web.archive.org/web/20080821163810/http://www.merriam-webster.com/dictionary/chicken |archive-date=August 21, 2008 }} In older sources, and still often in trade and scientific contexts, chickens as a species are described as common fowl or domestic fowl.{{cite book |last=Stevens |first=Lewis |title=Genetics and evolution of the domestic fowl |pages=11 and throughout |year=1991 |publisher=Cambridge University Press |isbn=978-0-521-40317-7 |url=https://books.google.com/books?id=S-DXqQ9UOmAC&dq=%22domestic+fowl%22&pg=PA11}}

{{multiple image

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Chickens are relatively large birds, active by day. The body is round, the legs are unfeathered in most breeds, and the wings are short. Wild junglefowl can fly; chickens and their flight muscles are too heavy to allow them to fly more than a short distance.{{cite web |last1=Geggel |first1=Laura |title=Forget About the Road. Why Are Chickens So Bad at Flying? |url=https://www.livescience.com/57139-why-chickens-cannot-fly.html |website=Live Science |access-date=February 3, 2024 |date=December 8, 2016 |archive-date=April 4, 2024 |archive-url=https://web.archive.org/web/20240404115622/https://www.livescience.com/57139-why-chickens-cannot-fly.html |url-status=live }} Size and coloration vary widely between breeds.{{cite web |title=Chicken |url=https://nationalzoo.si.edu/animals/domestic-chicken |publisher=Smithsonian's National Zoo & Conservation Biology Institute |access-date=February 2, 2024 |archive-date=February 2, 2024 |archive-url=https://web.archive.org/web/20240202165324/https://nationalzoo.si.edu/animals/domestic-chicken |url-status=live }} Newly-hatched chicks of both modern and heritage varieties weigh the same, about {{cvt|37|g|oz}}. Modern varieties however grow much faster; by day 35 a Ross 708 broiler may weigh {{cvt|1.8|kg|lb}} as against the {{cvt|1.05|kg|lb}} of a heritage chicken of the same age.{{cite journal |last1=Schmidt |first1=C.J. |last2=Persia |first2=M.E. |last3=Feierstein |first3=E. |last4=Kingham |first4=B. |last5=Saylor |first5=W.W. |title=Comparison of a modern broiler line and a heritage line unselected since the 1950s |journal=Poultry Science |volume=88 |issue=12 |date=2009 |doi=10.3382/ps.2009-00055 |doi-access=free |pages=2610–2619|pmid=19903960 }}

Adult chickens of both sexes have a fleshy crest on their heads called a comb or cockscomb, and hanging flaps of skin on either side under their beaks called wattles; combs and wattles are more prominent in males. Some breeds have a mutation that causes extra feathering under the face, giving the appearance of a beard.{{cite journal |last1=Guo |first1=Ying |last2=Gu |first2=Xiaorong |last3=Sheng |first3=Zheya |last4=Wang |first4=Yanqiang |last5=Luo |first5=Chenglong |last6=Liu |first6=Ranran |last7=Qu |first7=Hao |last8=Shu |first8=Dingming |last9=Wen |first9=Jie |last10=Crooijmans |first10=Richard P. M. A. |last11=Carlborg |first11=Örjan |last12=Zhao |first12=Yiqiang |last13=Hu |first13=Xiaoxiang |last14=Li |first14=Ning |display-authors=5 |title=A Complex Structural Variation on Chromosome 27 Leads to the Ectopic Expression of HOXB8 and the Muffs and Beard Phenotype in Chickens |journal=PLOS Genetics |volume=12 |issue=6 |date=June 2, 2016 |pmid=27253709 |pmc=4890787 |doi=10.1371/journal.pgen.1006071 |doi-access=free |page=e1006071}}

Chickens are omnivores.{{cite web |url=http://www.ideas-4-pets.co.uk/info.-on-chicken-care |title=Info on Chicken Care |access-date=August 13, 2008 |website=Ideas-4-pets.co.uk |year=2003 |archive-url=https://web.archive.org/web/20150625195044/http://www.ideas-4-pets.co.uk/info.-on-chicken-care |archive-date=June 25, 2015 |url-status=dead }} In the wild, they scratch at the soil to search for seeds, insects, and animals as large as lizards, small snakes,{{cite web |url=https://www.youtube.com/watch?v=45i1hZfUQhk |archive-url=https://ghostarchive.org/varchive/youtube/20211211/45i1hZfUQhk| archive-date=December 11, 2021 |url-status=live|title=Chicken Kills Rattlesnake |last=D Lines |date=July 27, 2013 |access-date=March 13, 2019 |publisher=YouTube}}{{cbignore}} and young mice.{{cite web |url=https://gworrell.freeyellow.com/chickenfaq.html |title=Frequently asked questions about chickens & eggs |access-date=August 13, 2008 |website=Gworrell.freeyellow.com |author=Gerard P.Worrell AKA "Farmer Jerry" |archive-url=https://web.archive.org/web/20080916202420/http://gworrell.freeyellow.com/chickenfaq.html |archive-date=September 16, 2008 |url-status=live }} A chicken may live for 5–10 years, depending on the breed.{{cite web |url=http://www.ruleworks.co.uk/cgi-bin/TUfaq.exe?Guide=Poultry&Category=Poultry%20-%20General#q9 |title=The Poultry Guide – A to Z and FAQs |website=Ruleworks.co.uk |access-date=August 29, 2010 |archive-url=https://web.archive.org/web/20101128085141/http://ruleworks.co.uk/cgi-bin/TUfaq.exe?Guide=Poultry&Category=Poultry%20-%20General#q9 |archive-date=November 28, 2010 |url-status=dead }} The world's oldest known chicken lived for 16 years.{{cite web|last1=Smith |first1=Jamon |url=https://www.tuscaloosanews.com/article/DA/20060806/News/606120381/TL |title=World's oldest chicken starred in magic shows, was on 'Tonight Show' |archive-url=https://web.archive.org/web/20190220002804/https://www.tuscaloosanews.com/apps/pbcs.dll/article?AID=%2F20060806%2FNEWS%2F608060400%2F1007%2FNEWS02 |archive-date=February 20, 2019 |website=Tuscaloosa News |location=Alabama, USA |date=August 6, 2006 |access-date=May 18, 2020 |url-status=live}}

Chickens are gregarious, living in flocks, and incubate eggs and raise young communally. Individual chickens dominate others, establishing a pecking order; dominant individuals take priority for access to food and nest sites. The concept of dominance, involving pecking, was described in female chickens by Thorleif Schjelderup-Ebbe in 1921 as the "pecking order".{{cite journal |last=Perrin |first=P. G. |year=1955 |title='Pecking order' 1927–54 |journal=American Speech |volume=30 |issue=4 |pages=265–268|doi=10.2307/453561 |jstor=453561 | issn = 0003-1283}}{{cite book |last=Schjelderup-Ebbe |first=T. |year=1975 |chapter=Contributions to the social psychology of the domestic chicken [Schleidt M., Schleidt, W. M., translators] |editor-last=Schein |editor-first=M. W. |title=Social Hierarchy and Dominance. Benchmark Papers in Animal Behavior |volume=3 |location=Stroudsburg, Pennsylvania |publisher=Dowden, Hutchinson and Ross |pages=35–49}} (Reprinted from Zeitschrift für Psychologie, 1922, 88:225–252.) Male chickens tend to leap and use their claws in conflicts.{{cite journal |last=Rajecki |first=D. W. |year=1988 |title=Formation of leap orders in pairs of male domestic chickens |journal=Aggressive Behavior |volume=14 |issue=6 |pages=425–436|doi=10.1002/1098-2337(1988)14:6<425::AID-AB2480140604>3.0.CO;2-#|s2cid=141664966 }} Chickens are capable of mobbing and killing a weak or inexperienced predator, such as a young fox.{{cite web |last=AFP |date=March 12, 2019 |title=Chickens 'teamed up to kill fox' at Brittany farming school |url=https://www.theguardian.com/world/2019/mar/12/chickens-teamed-up-to-kill-fox-at-brittany-farming-school |url-status=live |archive-url=https://web.archive.org/web/20190313002528/https://www.theguardian.com/world/2019/mar/12/chickens-teamed-up-to-kill-fox-at-brittany-farming-school |archive-date=March 13, 2019 |access-date=March 13, 2019 |website=Theguardian.com}}

File:Rooster_crowing_small.ogv

A male's crowing is a loud and sometimes shrill call, serving as a territorial signal to other males,{{Cite news |url=https://phys.org/news/2015-07-cock-roosters-crow.html |title=Top cock: Roosters crow in pecking order |website=Phys.org |access-date=January 14, 2018 |archive-url=https://web.archive.org/web/20180115124738/https://phys.org/news/2015-07-cock-roosters-crow.html |archive-date=January 15, 2018 |url-status=live }} and in response to sudden disturbances within their surroundings. Hens cluck loudly after laying an egg and to call their chicks. Chickens give different warning calls to indicate that a predator is approaching from the air or on the ground.{{cite journal |last1=Evans |first1=Christopher S. |last2=Evans |first2=Linda |last3=Marler |first3=Peter |title=On the meaning of alarm calls: functional reference in an avian vocal system |journal=Animal Behaviour |date=July 1993 |volume=46 |issue=1 |pages=23–38 |doi=10.1006/anbe.1993.1158 |s2cid=53165305 |s2cid-access=free }}

To initiate courting, some roosters may dance in a circle around or near a hen (a circle dance), often lowering the wing which is closest to the hen.{{cite book |title=Animals in Translation |last1=Grandin |first1=Temple |author-link1=Temple Grandin |last2=Johnson |first2=Catherine |year=2005 |publisher=Scribner's |location=New York City |isbn=978-0-7432-4769-6 |pages=[https://archive.org/details/animalsintransla00gran/page/69 69–71] |url-access=registration |url=https://archive.org/details/animalsintransla00gran/page/69 }} The dance triggers a response in the hen and when she responds to his call, the rooster may mount the hen and proceed with the mating. Mating typically involves a sequence in which the male approaches the female and performs a waltzing display. If the female is unreceptive, she runs off; otherwise, she crouches, and the male mounts, treading with both feet on her back. After copulation the male does a tail-bending display.{{cite journal |last1=Cheng |first1=Kimberly M. |last2=Burns |first2=Jeffrey T. |title=Dominance Relationship and Mating Behavior of Domestic Cocks: A Model to Study Mate-Guarding and Sperm Competition in Birds |journal=The Condor |date=August 1988 |volume=90 |issue=3 |pages=697–704 |doi=10.2307/1368360 |jstor=1368360 }}

Sperm transfer occurs by cloacal contact between the male and female, in an action called the 'cloacal kiss'.{{cite journal |last=Briskie |first=J. V. |author2=R. Montgomerie |year=1997 |title=Sexual Selection and the Intromittent Organ of Birds |journal=Journal of Avian Biology |volume=28 |issue=1 |pages=73–86 |doi=10.2307/3677097 |jstor=3677097}} As with all birds, reproduction is controlled by a neuroendocrine system,{{Cite journal |last1=Dufour |first1=Sylvie |last2=Quérat |first2=Bruno |last3=Tostivint |first3=Hervé |last4=Pasqualini |first4=Catherine |last5=Vaudry |first5=Hubert |last6=Rousseau |first6=Karine |date=April 2020 |title=Origin and Evolution of the Neuroendocrine Control of Reproduction in Vertebrates, With Special Focus on Genome and Gene Duplications |url=https://journals.physiology.org/doi/full/10.1152/physrev.00009.2019 |journal=Physiological Reviews |volume=100 |issue=2 |pages=869–943 |doi=10.1152/physrev.00009.2019 |pmid=31625459 |issn=0031-9333}} the Gonadotropin-Releasing Hormone-I neurons in the hypothalamus. Reproductive hormones including estrogen, progesterone, and gonadotropins (luteinizing hormone and follicle-stimulating hormone) initiate and maintain sexual maturation changes. Reproduction declines with age, thought to be due to a decline in GnRH-I-N.{{cite journal |last1=Bain |first1=M. M. |last2=Nys |first2=Y. |last3=Dunn |first3=I.C. |title=Increasing persistency in lay and stabilising egg quality in longer laying cycles. What are the challenges? |journal=British Poultry Science |publisher=Taylor & Francis |volume=57 |issue=3 |date=May 3, 2016 |doi=10.1080/00071668.2016.1161727 |pages=330–338 |pmid=26982003 |pmc=4940894 |s2cid=17842329 |doi-access=free }}

File:Newly-hatched chickens.jpg

Hens often try to lay in nests that already contain eggs and sometimes move eggs from neighbouring nests into their own. A flock thus uses only a few preferred locations, rather than having a different nest for every bird.{{cite journal |last1=Sherwin |first1=C.M. |last2=Nicol |first2=C.J. |year=1993 |title=Factors influencing floor-laying by hens in modified cages |journal=Applied Animal Behaviour Science |volume=36 |issue=2–3 |pages=211–222 |doi=10.1016/0168-1591(93)90011-d}} Under natural conditions, most birds lay only until a clutch is complete; they then incubate all the eggs. This is called "going broody". The hen sits on the nest, fluffing up or pecking defensively if disturbed. She rarely leaves the nest until the eggs have hatched.{{cite web |title=Why Do Chickens Puff up Their Feathers? I 4 Reasons Explained|date= August 8, 2020|url= https://chickenandchicksinfo.com/why-do-chickens-puff-up-their-feathers/ |access-date=June 16, 2021 |archive-date=June 18, 2021 |archive-url=https://web.archive.org/web/20210618091939/https://chickenandchicksinfo.com/why-do-chickens-puff-up-their-feathers/ |url-status=live}}

Eggs of chickens from the high-altitude region of Tibet have special physiological adaptations that result in a higher hatching rate in low oxygen environments. When eggs are placed in a hypoxic environment, chicken embryos from these populations express much more hemoglobin than embryos from other chicken populations. This hemoglobin has a greater affinity for oxygen, binding oxygen more readily.{{Cite journal |last1=Zhang |first1=H. |last2=Wang |first2=X.T. |last3=Chamba |first3=Y. |last4=Ling |first4=Y.|last5=Wu|first5=C.X. |date=October 2008|title=Influences of Hypoxia on Hatching Performance in Chickens with Different Genetic Adaptation to High Altitude |journal=Poultry Science |volume=87 |issue=10 |pages=2112–2116 |doi=10.3382/ps.2008-00122 |pmid=18809874 |doi-access=free}}

Fertile chicken eggs hatch at the end of the incubation period, about 21 days; the chick uses its egg tooth to break out of the shell. Hens remain on the nest for about two days after the first chick hatches; during this time the newly hatched chicks feed by absorbing the internal yolk sac.{{cite journal |last1=Ali |first1=A. |last2=Cheng |first2=K.M. |year=1985 |title=Early egg production in genetically blind (rc/rc) chickens in comparison with sighted (Rc+/rc) controls |journal=Poultry Science |volume=64 |issue=5 |pages=789–794 |doi=10.3382/ps.0640789 |pmid=4001066 |doi-access=free }} The hen guards her chicks and broods them to keep them warm. She leads them to food and water and calls them towards food. The chicks imprint on the hen and subsequently follow her continually. She continues to care for them until they are several weeks old.{{cite journal |last1=Edgar |first1=Joanne |last2=Held |first2=Suzanne |last3=Jones |first3=Charlotte |last4=Troisi |first4=Camille |title=Influences of Maternal Care on Chicken Welfare |journal=Animals |volume=6 |issue=1 |date=January 5, 2016 |pmid=26742081 |pmc=4730119 |doi=10.3390/ani6010002 |doi-access=free |page=2}}

Inbreeding of White Leghorn chickens tends to cause inbreeding depression expressed as reduced egg number and delayed sexual maturity.{{cite journal |last1=Sewalem |first1=A. |last2=Johansson |first2=K. |last3=Wilhelmson |first3=M. |last4=Lillpers |first4=K. |title=Inbreeding and inbreeding depression on reproduction and production traits of White Leghorn lines selected for egg production traits |journal=British Poultry Science |volume=40 |issue=2 |date=1999 |doi=10.1080/00071669987601 |pages=203–208|pmid=10465386 }} Strongly inbred Langshan chickens display obvious inbreeding depression in reproduction, particularly for traits such as age when the first egg is laid and egg number.{{cite journal |last1=Xue |first1=Qian |last2=Li |first2=Guohui |last3=Cao |first3=Yuxia |last4=Yin |first4=Jianmei |last5=Zhu |first5=Yunfen |last6=Zhang |first6=Huiyong |last7=Zhou |first7=Chenghao |last8=Shen |first8=Haiyu |last9=Dou |first9=Xinhong |last10=Su |first10=Yijun |last11=Wang |first11=Kehua |last12=Zou |first12=Jianmin |last13=Han |first13=Wei |title=Identification of genes involved in inbreeding depression of reproduction in Langshan chickens |journal=Animal Bioscience |volume=34 |issue=6 |date=June 1, 2021 |issn=2765-0189 |pmid=33152217 |pmc=8100482 |doi=10.5713/ajas.20.0248 |pages=975–984}}

File:Red Junglefowl.jpg, the wild ancestor of the chicken ]]

Water or ground-dwelling fowl similar to modern partridges, in the Galliformes, the order of bird that chickens belong to, survived the Cretaceous–Paleogene extinction event that killed all tree-dwelling birds and their dinosaur relatives.{{cite journal |last=Pennisi |first=Elizabeth |author-link=Elizabeth Pennisi |title=Quaillike creatures were the only birds to survive the dinosaur-killing asteroid impact |journal=Science |date=May 24, 2018 |doi=10.1126/science.aau2802}} Chickens are descended primarily from the red junglefowl (Gallus gallus) and are scientifically classified as the same species.{{cite journal |title=A genetic variation map for chicken with 2.8 million single nucleotide polymorphisms |journal=Nature |date=December 9, 2004 |volume=432 |issue=7018 |pages=717–722 |doi=10.1038/nature03156 |pmid=15592405 |pmc=2263125 |bibcode=2004Natur.432..717B |last1=Wong |first1=G. K. |last2=Liu |first2=B. |last3=Wang |first3=J. |last4=Zhang |first4=Y. |last5=Yang |first5=X. |last6=Zhang |first6=Z. |last7=Meng |first7=Q. |last8=Zhou |first8=J. |last9=Li |first9=D. |last10=Zhang |first10=J. |last11=Ni |first11=P. |last12=Li |first12=S. |display-authors=6}} Domesticated chickens freely interbreed with populations of red junglefowl. The domestic chicken has subsequently hybridised with grey junglefowl, Sri Lankan junglefowl and green junglefowl;{{cite journal |last1=Lawal |first1=Raman Akinyanju |last2=Martin |first2=Simon H. |last3=Vanmechelen |first3=Koen |last4=Vereijken |first4=Addie |last5=Silva |first5=Pradeepa |last6=Al-Atiyat |first6=Raed Mahmoud |last7=Aljumaah |first7=Riyadh Salah |last8=Mwacharo |first8=Joram M. |last9=Wu |first9=Dong-Dong |last10=Zhang |first10=Ya-Ping |last11=Hocking |first11=Paul M. |last12=Smith |first12=Jacqueline |last13=Wragg |first13=David |last14=Hanotte |first14=Olivier |display-authors=6 |title=The wild species genome ancestry of domestic chickens |journal=BMC Biology |date=December 2020 |volume=18 |issue=1 |pages=13 |doi=10.1186/s12915-020-0738-1 |pmid=32050971 |pmc=7014787 |doi-access=free}} a gene for yellow skin, for instance, was incorporated into domestic birds from the grey junglefowl (G. sonneratii).{{cite journal |last1=Eriksson |first1=Jonas |last2=Larson |first2=Greger |last3=Gunnarsson |first3=Ulrika |last4=Bed'hom |first4=Bertrand |last5=Tixier-Boichard |first5=Michele |last6=Strömstedt |first6=Lina |last7=Wright |first7=Dominic |last8=Jungerius |first8=Annemieke |last9=Vereijken |first9=Addie |last10=Randi |first10=Ettore |last11=Jensen |first11=Per |last12=Andersson |first12=Leif |display-authors=6 |title=Identification of the Yellow Skin Gene Reveals a Hybrid Origin of the Domestic Chicken |journal=PLOS Genetics |date=February 29, 2008 |volume=4 |issue=2 |pages=e1000010 |doi=10.1371/journal.pgen.1000010 |pmid=18454198 |pmc=2265484 |doi-access=free }} It is estimated that chickens share between 71 and 79% of their genome with red junglefowl.

{{further|Domestication}}

File:Chicken domestication and dispersal.svg

According to one early study, a single domestication event of the red junglefowl in present-day Thailand gave rise to the modern chicken with minor transitions separating the modern breeds.{{citation |title=One subspecies of the red junglefowl (Gallus gallus gallus) suffices as the matriarchic ancestor of all domestic breeds |first1=A. |last1=Fumihito |first2=T. |last2=Miyake |first3=S. |last3=Sumi |first4=M. |last4=Takada |first5=S. |last5=Ohno |first6=N. |last6=Kondo |journal=PNAS |date=December 20, 1994 |volume=91 |number=26 |pages=12505–12509 |doi=10.1073/pnas.91.26.12505 |pmid=7809067 |bibcode=1994PNAS...9112505F |pmc=45467 |doi-access=free }} The red junglefowl is well adapted to take advantage of the vast quantities of seed produced during the end of the multi-decade bamboo seeding cycle, to boost its own reproduction.{{citation |first=Rick |last=King |title=Rat Attack |date=February 24, 2009 |journal=Nova and National Geographic Television |url=https://www.pbs.org/wgbh/nova/nature/rat-attack.html |access-date=August 25, 2017 |archive-url=https://web.archive.org/web/20170823151419/http://www.pbs.org/wgbh/nova/nature/rat-attack.html |archive-date=August 23, 2017 |url-status=live }} In domesticating the chicken, humans took advantage of the red junglefowl's ability to reproduce prolifically when exposed to a surge in its food supply.{{citation |first=Rick |last=King |title=Plant vs. Predator |date=February 1, 2009 |journal=NOVA |url=https://www.pbs.org/wgbh/nova/nature/plant-vs-predator.html |access-date=August 25, 2017 |archive-url=https://web.archive.org/web/20170821123509/http://www.pbs.org/wgbh/nova/nature/plant-vs-predator.html |archive-date=August 21, 2017 |url-status=live }}

Exactly when and where the chicken was domesticated remains controversial. Genomic studies estimate that the chicken was domesticated 8,000 years ago in Southeast Asia and spread to China and India 2,000 to 3,000 years later. Archaeological evidence supports domestic chickens in Southeast Asia well before 6000 BC, China by 6000 BC and India by 2000 BC.{{cite journal |last1=West |first1=B. |last2=Zhou |first2=B.X. |year=1988 |title=Did chickens go north? New evidence for domestication |journal=J. Archaeol. Sci. |volume=14 |issue= 5 |pages=515–533 |doi=10.1016/0305-4403(88)90080-5 |bibcode=1988JArSc..15..515W }}{{cite journal |last1=Al-Nasser |first1=A. |last2=Al-Khalaifa |first2=H. |last3=Al-Saffar |first3=A. |last4=Khalil |first4=F. |last5=Albahouh |first5=M. |last6=Ragheb |first6=G. |last7=Al-Haddad |first7=A. |last8=Mashaly |first8=M. |title=Overview of chicken taxonomy and domestication |journal=World's Poultry Science Journal |date=June 1, 2007 |volume=63 |issue=2 |pages=285–300 |doi=10.1017/S004393390700147X |s2cid=86734013 }} A landmark 2020 Nature study that fully sequenced 863 chickens across the world suggests that all domestic chickens originate from a single domestication event of red junglefowl whose present-day distribution is predominantly in southwestern China, northern Thailand and Myanmar. These domesticated chickens spread across Southeast and South Asia where they interbred with local wild species of junglefowl, forming genetically and geographically distinct groups. Analysis of the most popular commercial breed shows that the White Leghorn breed possesses a mosaic of divergent ancestries inherited from subspecies of red junglefowl.{{cite journal |title=863 genomes reveal the origin and domestication of chicken |year=2020 |doi=10.1038/s41422-020-0349-y |s2cid=220050312 |last1=Wang |first1=Ming-Shan |last2=Thakur|first2=Mukesh |last3=Peng |first3=Min-Sheng |last4=Jiang |first4=Yu |last5=Frantz |first5=Laurent Alain François |last6=Li|first6=Ming |last7=Zhang|first7=Jin-Jin |last8=Wang |first8=Sheng |last9=Peters |first9=Joris |last10=Otecko |first10=Newton Otieno |last11=Suwannapoom |first11=Chatmongkon |last12=Guo |first12=Xing |journal=Cell Research |volume=30 |issue=8 |pages=693–701 |pmid=32581344 |pmc=7395088 |display-authors=6}}{{cite journal |last1=Liu |first1=Yi-Ping |last2=Wu |first2=Gui-Sheng |last3=Yao |first3=Yong-Gang |last4=Miao |first4=Yong-Wang |last5=Luikart |first5=Gordon |last6=Baig |first6=Mumtaz |last7=Beja-Pereira |first7=Albano |last8=Ding |first8=Zhao-Li |last9=Palanichamy |first9=Malliya Gounder |last10=Zhang |first10=Ya-Ping |display-authors=6 |title=Multiple maternal origins of chickens: Out of the Asian jungles |journal=Molecular Phylogenetics and Evolution |date=January 2006 |volume=38 |issue=1 |pages=12–19 |doi=10.1016/j.ympev.2005.09.014 |pmid=16275023 |bibcode=2006MolPE..38...12L }}{{cite journal |last1=Zeder |first1=Melinda A. |last2=Emshwiller |first2=Eve |last3=Smith |first3=Bruce D. |last4=Bradley |first4=Daniel G. |title=Documenting domestication: the intersection of genetics and archaeology |journal=Trends in Genetics |date=March 2006 |volume=22 |issue=3 |pages=139–155 |doi=10.1016/j.tig.2006.01.007 |pmid=16458995 }}

File:Map showing prehistoric diffusion of domestic chickens (Gallus gallus) into the Pacific via the Austronesian migrations (Thomson, Lebrasseur, & Austin, 2014).png from the Philippines via Neolithic Austronesian expansion (starting at c. 4000 BP), inferred from genetic markers on ancient and modern chicken DNA (Thomson et al., 2014)]]

A word for the domestic chicken (*manuk) is part of the reconstructed Proto-Austronesian language, indicating they were domesticated by the Austronesian peoples since ancient times. Chickens, together with dogs and pigs, were carried throughout the entire range of the prehistoric Austronesian maritime migrations to Island Southeast Asia, Micronesia, Island Melanesia, Polynesia, and Madagascar, starting from at least 3000 BC from Taiwan.{{cite journal |last=Thomson |first=Vicki A. |others= et al. |title=Using ancient DNA to study the origins and dispersal of ancestral Polynesian chickens across the Pacific |journal=Proceedings of the National Academy of Sciences |date=April 2014 |volume=111 |issue=13 |pages=4826–4831 |doi=10.1073/pnas.1320412111 |pmid=24639505 |pmc=3977275 |bibcode=2014PNAS..111.4826T |doi-access=free }}{{cite book |first1=Philip J. |last1=Piper |editor1-first=Philip J. |editor1-last=Piper |editor2-first=Hirofumi |editor2-last=Matsumura |editor3-first=David |editor3-last=Bulbeck |title=New Perspectives in Southeast Asian and Pacific Prehistory |chapter=The Origins and Arrival of the Earliest Domestic Animals in Mainland and Island Southeast Asia: A Developing Story of Complexity |publisher=ANU Press |volume=45 |series=terra australis |year=2017 |isbn=9781760460945 |chapter-url =http://press-files.anu.edu.au/downloads/press/n2320/html/ch15.xhtml |access-date =May 5, 2023 |archive-date =November 28, 2022 |archive-url =https://web.archive.org/web/20221128075413/https://press-files.anu.edu.au/downloads/press/n2320/html/ch15.xhtml |url-status =live}}{{cite book |url=https://books.google.com/books?id=FJ9ULYwX3zgC&pg=PA56 |title=The Cambridge History of the Pacific Islanders |first=Malama |last=Meleisea |date=March 25, 2004 |publisher=Cambridge University Press |page=56 |access-date=March 13, 2019 |archive-url=https://web.archive.org/web/20160913140948/https://books.google.com/books?id=FJ9ULYwX3zgC&pg=PA56 |archive-date=September 13, 2016 |url-status=live |isbn=9780521003544}}{{cite book |url=https://books.google.com/books?id=tlSspaBLkhoC&pg=PA411 |title=Anthropological Genetics: Theory, Methods and Applications |first=Michael H. |last=Crawford |date=March 13, 2019 |publisher=Cambridge University Press |page=411 |access-date=March 13, 2019 |via=Google Books |archive-url=https://web.archive.org/web/20160913143140/https://books.google.com/books?id=tlSspaBLkhoC&pg=PA411 |archive-date=September 13, 2016 |url-status=live |isbn=9780521546973}} These chickens may have been introduced during pre-Columbian times to South America via Polynesian seafarers, but this is disputed.{{cite news |last=Neumann |first=Scott |title=Study: The Chicken Didn't Cross The Pacific To South America |url=https://www.npr.org/sections/thetwo-way/2014/03/18/291182073/study-the-chicken-didnt-cross-the-pacific-to-south-america |access-date=May 5, 2023 |work=The Two Way |agency=NPR |date=March 18, 2014 |archive-date=May 5, 2023 |archive-url=https://web.archive.org/web/20230505060006/https://www.npr.org/sections/thetwo-way/2014/03/18/291182073/study-the-chicken-didnt-cross-the-pacific-to-south-america |url-status=live }}

The possibility that domestic chickens were in the Americas before Western contact is debated by researchers, but blue-egged chickens, found only in the Americas and Asia, suggest an Asian origin for early American chickens. A lack of data from Thailand, Russia, the Indian subcontinent, Southeast Asia and Sub-Saharan Africa makes it difficult to lay out a clear map of the spread of chickens in these areas; better description and genetic analysis of local breeds threatened by extinction may also help with research into this area. Chicken bones from the Arauco Peninsula in south-central Chile were radiocarbon dated as pre-Columbian, and DNA analysis suggested they were related to prehistoric populations in Polynesia.{{cite journal |last1=Borrell |first1=Brendan |title=DNA reveals how the chicken crossed the sea |journal=Nature |date=June 1, 2007 |volume=447 |issue=7145 |pages=620–621 |doi=10.1038/447620b |pmid=17554271 |bibcode=2007Natur.447R.620B |s2cid=4418786 |doi-access=free }}{{cite journal |last=Storey |first=A. A. |others= et al. |title=Radiocarbon and DNA evidence for a pre-Columbian introduction of Polynesian chickens to Chile |journal=Proceedings of the National Academy of Sciences |date=June 19, 2007 |volume=104 |issue=25 |pages=10335–10339 |doi=10.1073/pnas.0703993104 |pmid=17556540 |pmc=1965514 |bibcode=2007PNAS..10410335S |doi-access=free }} However, further study of the same bones cast doubt on the findings.{{cite journal |last=Gongora |first=Jaime |others= et al. |year=2008 |title=Indo-European and Asian origins for Chilean and Pacific chickens revealed by mtDNA |journal=PNAS |volume=105 |issue=30 |pages=10308–10313 |doi=10.1073/pnas.0801991105 |pmid=18663216 |pmc=2492461 |bibcode=2008PNAS..10510308G |doi-access=free }}{{cite journal |last=Thomson |first=Vicki A.

|others= et al. |title=Using ancient DNA to study the origins and dispersal of ancestral Polynesian chickens across the Pacific |journal=Proceedings of the National Academy of Sciences |date=April 1, 2014 |volume=111 |issue=13 |pages=4826–4831 |doi=10.1073/pnas.1320412111 |pmid=24639505 |pmc=3977275 |bibcode=2014PNAS..111.4826T |doi-access=free }}

Chicken remains have been difficult to date, given the small and fragile bird bones; this may account for discrepancies in dates given by different sources. Archaeological evidence is supplemented by mentions in historical texts from the last few centuries BC, and by depictions in prehistoric artworks, such as across Central Asia.{{cite journal |last=Peters |first=Carli |others= et al. |title= Archaeological and molecular evidence for ancient chickens in Central Asia |journal= Nature Communications |volume=15 |issue=1 |date=April 2, 2024 |page=2697 |issn=2041-1723 |pmid=38565545 |pmc=10987595 |doi=10.1038/s41467-024-46093-2|bibcode=2024NatCo..15.2697P }} Chickens were widespread throughout southern Central Asia by the 4th century BC.

Middle Eastern chicken remains go back to a little earlier than 2000 BC in Syria.The Cambridge History of Food, 2000, Cambridge University Press, Vol. 1, pp. 496–499 Phoenicians spread chickens along the Mediterranean coasts as far as Iberia. During the Hellenistic period (4th–2nd centuries BC), in the southern Levant, chickens began to be widely domesticated for food.{{cite journal |last1=Perry-Gal |first1=Lee |last2=Erlich |first2=Adi |last3=Gilboa |first3=Ayelet |last4=Bar-Oz |first4=Guy |date=August 11, 2015 |title=Earliest economic exploitation of chicken outside East Asia: Evidence from the Hellenistic Southern Levant |journal=Proceedings of the National Academy of Sciences |volume=112 |issue=32 |pages=9849–9854 |bibcode=2015PNAS..112.9849P |doi=10.1073/pnas.1504236112 |pmc=4538678 |pmid=26195775 |doi-access=free}} The first pictures of chickens in Europe are found on Corinthian pottery of the 7th century BC.{{cite book |url=https://books.google.com/books?id=NrIapgM4LwQC&pg=PA176 |title=Regional Greek Cooking |first1=Dean |last1=Karayanis |first2=Catherine |last2=Karayanis |date=March 13, 2019 |publisher=Hippocrene Books |page=176 |access-date=March 13, 2019 |via=Google Books |archive-url=https://web.archive.org/web/20160913141141/https://books.google.com/books?id=NrIapgM4LwQC&pg=PA176 |archive-date=September 13, 2016 |url-status=live |isbn=9780781811460}}{{cite book |url=https://books.google.com/books?id=Xwq1lunLkuoC&pg=PA207 |title=Cooking with the Bible: Biblical Food, Feasts, and Lore |first1=Anthony F. |last1=Chiffolo |first2=Rayner W. |last2=Hesse |date=March 13, 2019 |publisher=Greenwood Publishing Group |page=207 |access-date=March 13, 2019 |via=Google Books |archive-url=https://web.archive.org/web/20160913080305/https://books.google.com/books?id=Xwq1lunLkuoC&pg=PA207 |archive-date=September 13, 2016 |url-status=live |isbn=9780313334108}}

Breeding increased under the Roman Empire and reduced in the Middle Ages. Genetic sequencing of chicken bones from archaeological sites in Europe revealed that in the High Middle Ages chickens became less aggressive and began to lay eggs earlier in the breeding season.{{cite journal |last1=Brown |first1=Marley |title=Fast Food |journal=Archaeology |date=Sep–Oct 2017 |volume=70 |issue=5 |page=18 |url=https://www.archaeology.org/issues/269-1709/from-the-trenches/5820-trenches-europe-chicken-domestication |access-date=July 25, 2019 |issn=0003-8113 |archive-date=July 25, 2019 |archive-url=https://web.archive.org/web/20190725160925/https://www.archaeology.org/issues/269-1709/from-the-trenches/5820-trenches-europe-chicken-domestication |url-status=live }}

File:A Brown Hen.jpg

Chickens reached Egypt via the Middle East for purposes of cockfighting about 1400 BC and became widely bred in Egypt around 300 BC. Three possible routes of introduction into Africa around the early first millennium AD could have been through the Egyptian Nile Valley, the East Africa Roman-Greek or Indian trade, or from Carthage and the Berbers, across the Sahara. The earliest known remains are from Mali, Nubia, East Coast, and South Africa and date back to the middle of the first millennium AD.

{{main |Poultry disease}}

File:Pesse oujheas H9N2 tanfla.JPG ]]

Chickens are susceptible both to parasites such as mites, and to diseases caused by pathogens such as bacteria and viruses. The parasite Dermanyssus gallinae feeds on blood, causing irritation and reducing egg production, and acts as a vector for bacterial diseases such as salmonellosis and spirochaetosis.{{Cite journal |last1=Schiavone |first1=Antonella |last2=Pugliese |first2=Nicola |last3=Otranto |first3=Domenico |last4=Samarelli |first4=Rossella |last5=Circella |first5=Elena |last6=De Virgilio |first6=Caterina |last7=Camarda |first7=Antonio |date=January 20, 2022 |title=Dermanyssus gallinae: the long journey of the poultry red mite to become a vector |journal=Parasites & Vectors |volume=15 |issue=1 |pages=29 |doi=10.1186/s13071-021-05142-1 |pmid=35057849 |issn=1756-3305 |pmc=8772161 |doi-access=free }}

Viral diseases include avian influenza.{{cite journal |last1=Barjesteh |first1=Neda |last2=O'Dowd |first2=Kelsey |last3=Vahedi |first3=Seyed Milad |title=Antiviral responses against chicken respiratory infections: Focus on avian influenza virus and infectious bronchitis virus |journal=Cytokine |date=March 2020 |volume=127 |pages=154961 |doi=10.1016/j.cyto.2019.154961 |pmid=31901597|pmc=7129915 }}

{{Main|Poultry farming}}

Chickens are common and widespread domestic animals, with a total population of 23.7 billion {{As of|2018|lc=y}}.{{cite web|title=Number of chickens worldwide from 1990 to 2018.|url=https://www.statista.com/statistics/263962/number-of-chickens-worldwide-since-1990/|access-date=February 23, 2020|website=Statista|archive-date=November 27, 2020|archive-url=https://web.archive.org/web/20201127124744/https://www.statista.com/statistics/263962/number-of-chickens-worldwide-since-1990/|url-status=live}} More than 50 billion chickens are reared annually as a source of meat and eggs.{{Cite web |url=https://www.ciwf.org.uk/farm-animals/chickens/ |title=About chickens |publisher=Compassion in World Farming |access-date=April 25, 2017 |archive-url=https://web.archive.org/web/20170426063521/https://www.ciwf.org.uk/farm-animals/chickens/ |archive-date=April 26, 2017 |url-status=live }} In the United States alone, more than 8 billion chickens are slaughtered each year for meat,{{Cite web |url=https://usda.library.cornell.edu/concern/publications/pg15bd88s |title=Poultry Slaughter Annual Summary |last=Fereira |first=John |website=usda.mannlib.cornell.edu |access-date=April 25, 2017 |archive-url=https://web.archive.org/web/20170426063701/http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do?documentID=1497 |archive-date=April 26, 2017 |url-status=live }} and more than 300 million chickens are reared for egg production.{{Cite web |url=https://usda.library.cornell.edu/concern/publications/1v53jw96n |title=Chickens and Eggs Annual Summary |last=Fereira |first=John |website=usda.mannlib.cornell.edu |access-date=April 25, 2017 |archive-url=https://web.archive.org/web/20170426061324/http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do?documentID=1509 |archive-date=April 26, 2017 |url-status=live }} The vast majority of poultry is raised in factory farms. According to the Worldwatch Institute, 74% of the world's poultry meat and 68% of eggs are produced this way.{{cite web |title=Towards Happier Meals In A Globalized World |url=http://www.worldwatch.org/towards-happier-meals-globalized-world |publisher=Worldwatch Institute |access-date=May 29, 2014 |archive-url=https://web.archive.org/web/20140529153518/http://www.worldwatch.org/towards-happier-meals-globalized-world |archive-date=May 29, 2014 |url-status=dead }} An alternative to intensive poultry farming is free-range farming. Friction between these two main methods has led to long-term issues of ethical consumerism. Opponents of intensive farming argue that it harms the environment, creates human health risks and is inhumane towards sentient animals.{{cite journal |last1=Ilea |first1=Ramona Cristina |title=Intensive Livestock Farming: Global Trends, Increased Environmental Concerns, and Ethical Solutions |journal=Journal of Agricultural and Environmental Ethics |date=April 2009 |volume=22 |issue=2 |pages=153–167 |doi=10.1007/s10806-008-9136-3 |bibcode=2009JAEE...22..153I |s2cid=154306257 }} Advocates of intensive farming say that their efficient systems save land and food resources owing to increased productivity, and that the animals are looked after in a controlled environment.{{cite journal |last1=Tilman |first1=David |last2=Cassman |first2=Kenneth G. |last3=Matson |first3=Pamela A. |last4=Naylor |first4=Rosamond |last5=Polasky |first5=Stephen |title=Agricultural sustainability and intensive production practices |journal=Nature |date=August 2002 |volume=418 |issue=6898 |pages=671–677 |doi=10.1038/nature01014 |pmid=12167873 |bibcode=2002Natur.418..671T |s2cid=3016610 }} Chickens farmed for meat are called broilers. Broiler breeds typically take less than six weeks to reach slaughter size,{{cite web |url=https://www.animalsaustralia.org/factsheets/broiler_chickens.php |title=Broiler Chickens Fact Sheet |website=Animals Australia |access-date=August 29, 2010 |archive-url=https://web.archive.org/web/20100712123234/http://www.animalsaustralia.org/factsheets/broiler_chickens.php |archive-date=July 12, 2010 |url-status=live }} some weeks longer for free range and organic broilers.{{cite web |title=Chickens Farmed for Meat |url=https://www.ciwf.org.uk/farm-animals/chickens/meat-chickens/ |publisher=Compassion in World Farming |access-date=February 2, 2024 |archive-date=September 21, 2024 |archive-url=https://web.archive.org/web/20240921105646/https://www.ciwf.org.uk/farm-animals/chickens/meat-chickens/ |url-status=live }}

File:Florida chicken house.jpg

Chickens farmed primarily for eggs are called layer hens. The UK alone consumes more than 34 million eggs per day.{{Cite web |url=https://www.egginfo.co.uk/egg-facts-and-figures/industry-information/data |title=UK Egg Industry Data |website=Official Egg Info |access-date=April 25, 2017 |archive-url=https://web.archive.org/web/20161230000509/https://www.egginfo.co.uk/egg-facts-and-figures/industry-information/data |archive-date=December 30, 2016 |url-status=live }} Hens of some breeds can produce over 300 eggs per year; the highest authenticated rate of egg laying is 371 eggs in 364 days.{{cite book |last1=Glenday |first1=Craig |title=Guinness World Records 2011 |date=April 26, 2011 |publisher=Jim Pattison Group |isbn=978-0440423102 |page=286}} After 12 months of laying, the commercial hen's egg-laying ability declines to the point where the flock is commercially unviable. Hens, particularly from battery cage systems, are sometimes infirm or have lost a significant amount of their feathers, and their life expectancy has been reduced from around seven years to less than two years.{{cite news |url=https://www.theguardian.com/lifeandstyle/2002/mar/10/foodanddrink.features1 |work=The Guardian |location=London |title=Ten weeks to live |first=Anthony |last=Browne |date=March 10, 2002 |access-date=April 28, 2010 |archive-url=https://web.archive.org/web/20080516080228/http://observer.guardian.co.uk/foodmonthly/story/0,,662799,00.html |archive-date=May 16, 2008 |url-status=live }} In the UK and Europe, laying hens are then slaughtered and used in processed foods, or sold as 'soup hens'. In some other countries, flocks are sometimes force moulted rather than being slaughtered to re-invigorate egg-laying. This involves complete withdrawal of food (and sometimes water) for 7–14 days{{cite journal |last1=Patwardhan |first1=D. |last2=King |first2=A. |year=2011 |title=Review: feed withdrawal and non feed withdrawal moult |journal=World's Poultry Science Journal |volume=67 |issue=2 |pages=253–268 |doi=10.1017/s0043933911000286|s2cid=88353703 }} or sufficiently long to cause a body weight loss of 25 to 35%,{{cite journal |last1=Webster |first1=A.B. |year=2003 |title=Physiology and behavior of the hen during induced moult |journal=Poultry Science |volume=82 |issue=6 |pages=992–1002 |doi=10.1093/ps/82.6.992 |pmid=12817455|doi-access=free }} or up to 28 days under experimental conditions.{{cite journal |last1=Molino |first1=A.B. |last2=Garcia |first2=E.A. |last3=Berto |first3=D.A. |last4=Pelícia |first4=K. |last5=Silva |first5=A.P. |last6=Vercese |first6=F. |year=2009 |title=The Effects of Alternative Forced-Molting Methods on The Performance and Egg Quality of Commercial Layers |journal=Brazilian Journal of Poultry Science |volume=11 |issue=2 |pages=109–113 |doi=10.1590/s1516-635x2009000200006|doi-access=free |hdl=11449/14340 |hdl-access=free }} This stimulates the hen to lose her feathers but also re-invigorates egg-production. Some flocks may be force-moulted several times. In 2003, more than 75% of all flocks were moulted in the US.{{cite journal |last1=Yousaf |first1=M. |last2=Chaudhry |first2=A.S. |title=History, changing scenarios and future strategies to induce moulting in laying hens |journal=World's Poultry Science Journal |date=March 1, 2008 |volume=64 |issue=1 |pages=65–75 |doi=10.1017/s0043933907001729 |s2cid=34761543 |url=http://eprint.ncl.ac.uk/file_store/production/56559/452E6892-26EF-40C6-891B-048E9FE17D2E.pdf |access-date=October 23, 2020 |archive-date=November 24, 2020 |archive-url=https://web.archive.org/web/20201124090812/https://eprint.ncl.ac.uk/file_store/production/56559/452E6892-26EF-40C6-891B-048E9FE17D2E.pdf |url-status=live }} Chickens are one of the most efficient sources of foods for many different purposes.

File:A 95 year old woman with her pet rooster, Havana, Cuba.jpg

{{seealso|Urban chicken keeping}}

Keeping chickens as pets became increasingly popular in the 2000s{{cite news |title=Some homeowners find chickens all the rage |work=Chicago Tribune |date=July 27, 2007 |last=Fly |first=Colin |url=https://pqasb.pqarchiver.com/chicagotribune/access/1310840201.html?.dids=1310840201:1310840201&FMT=ABS&FMTS=ABS:FT&type=current&date=Jul+27,+2007&author=Colin+Fly&pub=Chicago+Tribune&desc=Some+homeowners+find+chickens+all+the+rage&pqatl=google }}{{dead link|date=July 2024|bot=medic}}{{cbignore|bot=medic}} among urban and suburban residents.{{cite news |title=Cooped up in suburbia |work=Boston Globe |date=December 16, 2004 |last=Pollack-Fusi |first=Mindy |url=https://www.boston.com/yourlife/home/articles/2004/12/16/cooped_up_in_suburbia/ |access-date=June 4, 2020 |archive-date=March 4, 2016 |archive-url=https://web.archive.org/web/20160304063550/http://www.boston.com/yourlife/home/articles/2004/12/16/cooped_up_in_suburbia/ |url-status=live }} Many people obtain chickens for their egg production but often name them and treat them as any other pet like cats or dogs. Chickens provide companionship and have individual personalities. While many do not cuddle much, they will eat from one's hand, jump onto one's lap, respond to and follow their handlers, as well as show affection.{{Cite news|url=https://www.nytimes.com/2020/11/25/magazine/backyard-chickens-empathy.html |archive-url=https://web.archive.org/web/20201125101336/https://www.nytimes.com/2020/11/25/magazine/backyard-chickens-empathy.html |archive-date=November 25, 2020 |url-access=subscription |url-status=live|title = How Caring for Backyard Chickens Stretched My Emotional Muscles|newspaper = The New York Times|date = November 25, 2020|last1 = Kreilkamp|first1 = Ivan}}{{Cite web|url=https://www.latimes.com/style/pets/la-hm-pets-chickens-20170827-story.html|title=Chickens will become a beloved pet — just like the family dog|last=Boone|first=Lisa|website=Los Angeles Times|date=August 27, 2017|access-date=April 3, 2019|archive-date=April 2, 2019|archive-url=https://web.archive.org/web/20190402104824/https://www.latimes.com/style/pets/la-hm-pets-chickens-20170827-story.html|url-status=live}} Chickens are social, inquisitive, intelligent{{Cite web|last=Barras|first=Colin|title=Despite what you might think, chickens are not stupid|url=https://www.bbc.com/earth/story/20170110-despite-what-you-might-think-chickens-are-not-stupid|archive-url=https://web.archive.org/web/20210605084929/https://www.bbc.com/earth/story/20170110-despite-what-you-might-think-chickens-are-not-stupid|archive-date=June 5, 2021|access-date=September 6, 2020|website=www.bbc.com|language=en}} birds, and many people find their behaviour entertaining.{{cite web |url=https://www.upc-online.org/home.html |title=Providing a Good Home for Chickens |author=United Poultry Concerns |access-date=May 4, 2009 |archive-url=https://web.archive.org/web/20090605061816/http://www.upc-online.org/home.html |archive-date=June 5, 2009 |url-status=live }} Certain breeds, such as silkies and many bantam varieties, are generally docile and are often recommended as good pets around children with disabilities.{{cite web |url=https://www.henkeeping.co.uk/henkeeping/choosing-your-chickens/ |website=Clucks and Chooks |title=Choosing Your Chickens |url-status=live |archive-url=https://web.archive.org/web/20090730222405/http://www.henkeeping.co.uk/which.html |archive-date=July 30, 2009}}

{{main|Cockfight}}

File:COCK FIGHT.JPG in Tamil Nadu, India, 2011 ]]

A cockfight is a contest held in a ring called a cockpit between two cocks. Cockfighting is outlawed in many countries as involving cruelty to animals.{{cite news|author=Raymond Hernandez |url=https://www.nytimes.com/1995/04/11/nyregion/blood-sport-gets-blood-fans-cockfighting-don-t-understand-its-outlaw-status.html?pagewanted=all&src=pm |title=A Blood Sport Gets in the Blood; Fans of Cockfighting Don't Understand Its Outlaw Status |work=The New York Times |location=New York City Metropolitan Area |date=April 11, 1995 |access-date=May 10, 2014}} The activity seems to have been practised in the Indus Valley civilisation from 2500 to 2100 BC.{{cite book |last=Crawford |first=R. D. |title=Poultry Breeding and Genetics |publisher=Elsevier |year=1990 |pages=10–11 |isbn=978-0444885579 |ol=2207173M |url=https://openlibrary.org/books/OL2207173M/Poultry_breeding_and_genetics |access-date=February 2, 2024 |archive-date=April 18, 2023 |archive-url=https://web.archive.org/web/20230418123608/https://openlibrary.org/books/OL2207173M/Poultry_breeding_and_genetics |url-status=live }} In the process of domestication, chickens were apparently kept initially for cockfighting, and only later used for food.{{cite journal |last1=Lawler |first1=Andrew |last2=Adler |first2=Jerry |title=How the Chicken Conquered the World |journal=Smithsonian Magazine |issue=June 2012 |date=June 2012 |url=http://www.smithsonianmag.com/history/how-the-chicken-conquered-the-world-87583657/ |access-date=February 2, 2024 |archive-date=October 31, 2019 |archive-url=https://web.archive.org/web/20191031040210/https://www.smithsonianmag.com/history/how-the-chicken-conquered-the-world-87583657/ |url-status=live }}

Chickens have long been used as model organisms to study developing embryos. Large numbers of embryos can be provided commercially; fertilized eggs can easily be opened and used to observe the developing embryo. Equally important, embryologists can carry out experiments on such embryos, close the egg again and study the effects later in development. For instance, many important discoveries in limb development have been made using chicken embryos, such as the discovery of the apical ectodermal ridge and the zone of polarizing activity.{{cite journal |last1=Young |first1=John J. |last2=Tabin |first2=Clifford J. |title=Saunders's framework for understanding limb development as a platform for investigating limb evolution |journal=Developmental Biology |date=September 2017 |volume=429 |issue=2 |pages=401–408 |doi=10.1016/j.ydbio.2016.11.005 |pmid=27840200 |pmc=5426996 }}

The chicken was the first bird species to have its genome sequenced.{{cite journal |author=International Chicken Genome Sequencing Consortium |title=Sequence and comparative analysis of the chicken genome provide unique perspectives on vertebrate evolution |journal=Nature |date=December 9, 2004 |volume=432 |issue=7018 |pages=695–716 |doi=10.1038/nature03154 |pmid=15592404 |bibcode=2004Natur.432..695C |doi-access=free }} At 1.21 Gb, the chicken genome is similarly sized compared to other birds, but smaller than nearly all mammals: the human genome is 3.2 Gb.{{cite journal |last1=Gregory |first1=T. Ryan |title=Synergy between sequence and size in Large-scale genomics |journal=Nature Reviews Genetics |date=September 2005 |volume=6 |issue=9 |pages=699–708 |doi=10.1038/nrg1674|pmid=16151375 |s2cid=24237594 }} The final gene set contained 26,640 genes (including noncoding genes and pseudogenes), with a total of 19,119 protein-coding genes, a similar number to the human genome.{{cite journal |last1=Warren |first1=Wesley C. |last2=Hillier |first2=LaDeana W. |last3=Tomlinson |first3=Chad |last4=Minx |first4=Patrick |last5=Kremitzki |first5=Milinn |last6=Graves |first6=Tina |last7=Markovic |first7=Chris |last8=Bouk |first8=Nathan |last9=Pruitt |first9=Kim D. |last10=Thibaud-Nissen |first10=Francoise |last11=Schneider |first11=Valerie |last12=Mansour |first12=Tamer A. |display-authors=6 |title=A New Chicken Genome Assembly Provides Insight into Avian Genome Structure |journal=G3 |date=January 2017 |volume=7 |issue=1 |pages=109–117 |doi=10.1534/g3.116.035923 |pmid=27852011 |pmc=5217101 }} In 2006, scientists researching the ancestry of birds switched on a chicken recessive gene, talpid2, and found that the embryo jaws initiated formation of teeth, like those found in ancient bird fossils.[https://abcnews.go.com/Technology/story?id=1666805 Scientists Find Chickens Retain Ancient Ability to Grow Teeth] {{Webarchive|url=https://web.archive.org/web/20080620230515/https://abcnews.go.com/Technology/story?id=1666805 |date=June 20, 2008 }} Ammu Kannampilly, ABC News, February 27, 2006. Retrieved October 1, 2007.

{{Anchor|Crowing|Cockadoodledoo|Cocka-doodle-doo}}

{{main|Cultural references to chickens}}

Chickens are featured widely in folklore, religion, literature, and popular culture. The chicken is a sacred animal in many cultures and deeply embedded in belief systems and religious practices.{{cite magazine |last1=Adler |first1=Jerry |last2=Lawler |first2=Andrew |date=June 2012 |title=How the Chicken Conquered the World |url=https://www.smithsonianmag.com/history/how-the-chicken-conquered-the-world-87583657/ |magazine=Smithsonian |access-date=May 24, 2012 |archive-url=https://web.archive.org/web/20121103193648/http://www.smithsonianmag.com/history-archaeology/How-the-Chicken-Conquered-the-World.html |archive-date=November 3, 2012 |url-status=live}}

Roosters are sometimes used for divination, a practice called alectryomancy. This involves the sacrifice of a sacred rooster, often during a ritual cockfight, used as a form of communication with the gods.{{cite book |url=https://books.google.com/books?id=vvVPAAAAMAAJ&q=Alectryomancy+cockfight&pg=PA394 |title=Encyclopædia Perthensis; Or Universal Dictionary of the Arts, Sciences, Literature, &c. Intended to Supersede the Use of Other Books of Reference |publisher=John Brown |year=1816 |edition=2nd |volume=1 |page=394 |access-date=February 2, 2024 |archive-date=September 21, 2024 |archive-url=https://web.archive.org/web/20240921105802/https://books.google.com/books?id=vvVPAAAAMAAJ&q=Alectryomancy+cockfight&pg=PA394#v=snippet&q=Alectryomancy%20cockfight&f=false |url-status=live }} In Gabriel García Márquez's Nobel-Prize-winning 1967 novel One Hundred Years of Solitude, cockfighting is outlawed in the town of Macondo after the patriarch of the Buendia family murders his cockfighting rival and is haunted by the man's ghost.{{cite news |title=Love and Immolation in Argentina |url=https://www.washingtonpost.com/archive/entertainment/books/1981/08/16/love-and-immolation-in-argentina/9cf0bdac-cfc3-4198-8824-d89d5e059c55/ |newspaper=Washington Post |date=August 16, 1981 |access-date=February 2, 2024 |archive-date=August 27, 2017 |archive-url=https://web.archive.org/web/20170827142619/https://www.washingtonpost.com/archive/entertainment/books/1981/08/16/love-and-immolation-in-argentina/9cf0bdac-cfc3-4198-8824-d89d5e059c55/ |url-status=live }} Chicken jokes have been made at least since The Knickerbocker published one in 1847.The Knickerbocker, or The New York Monthly, March 1847, p. 283. Chickens have been featured in art in farmyard scenes such as Adriaen van Utrecht's 1646 Turkeys and Chickens and Walter Osborne's 1885 Feeding the Chickens.{{cite web |last1=Kellogg |first1=Diane M. |title=Chickens in Art History |url=https://www.paintingworldmag.com/post/chickens-in-art-history |publisher=Painting World Magazine |access-date=February 2, 2024 |date=May 22, 2020 |archive-date=February 2, 2024 |archive-url=https://web.archive.org/web/20240202161615/https://www.paintingworldmag.com/post/chickens-in-art-history |url-status=dead }} The nursery rhyme "Cock a doodle doo", its chorus line imitating the cockerel's call, was published in Mother Goose's Melody in 1765.{{cite book |last1=Opie |first1=Iona |last2=Opie |first2=Peter |title=The Oxford Dictionary of Nursery Rhymes |publisher=Oxford University Press |orig-year=1951 |edition=2nd |year=1997 |page=128}}

The 2000 animated adventure comedy film Chicken Run, directed by Peter Lord and Nick Park, featured anthropomorphic chickens with many chicken jokes.{{cite magazine |last=Corliss |first=Richard |date=December 4, 2000 |title=Run, Chicken Run! |language=en-US |magazine=Time |url=https://content.time.com/time/world/article/0,8599,2047283,00.html |access-date=March 23, 2023 |issn=0040-781X |archive-date=January 24, 2023 |archive-url=https://web.archive.org/web/20230124033415/https://content.time.com/time/world/article/0,8599,2047283,00.html |url-status=live }}{{Cite web|url=https://catalog.afi.com/Catalog/moviedetails/61096|title=AFI|Catalog|access-date=August 17, 2018|archive-date=August 17, 2018|archive-url=https://web.archive.org/web/20180817060102/https://catalog.afi.com/Catalog/moviedetails/61096|url-status=live}}{{Cite web |url=https://www.sfgate.com/movies/amp/Chicken-Recipe-Simply-Divine-Action-comedy-3239861.php|title='Chicken' Recipe Simply Divine / Action comedy blends great story, animation |website=SFGate |date=June 21, 2000 |access-date=June 2, 2021 |archive-date=June 2, 2021 |archive-url=https://web.archive.org/web/20210602214504/https://www.sfgate.com/movies/amp/Chicken-Recipe-Simply-Divine-Action-comedy-3239861.php |url-status=live}}

File:Terracotta askos (flask) in the form of a rooster MET DP252108 (cropped).jpg|Etruscan askos in the form of a rooster, 4th century B.C.

File:Rooster and hen, Dong Ho picture, paper - Vietnam National Museum of Fine Arts - Hanoi, Vietnam - DSC05287.JPG|Rooster and hen, Đông Hồ folk woodcut, Vietnam

File:Feeding the chickens, by Walter Frederick Osborne.jpg|Feeding the chickens by Walter Osborne, 1885

File:Joseph Crawhall - Spanish Cock And Snail.jpg|Joseph Crawhall III, Spanish Cock and Snail, c. 1900

File:Chicken Mask Bali.jpg|Wooden chicken mask, Bali, late 20th century

File:Yoruba Cockfight.jpg|Carved and painted wooden tribal statue of a cock fight, Yoruba, West Africa, c. 2000

File:France-001717 - Gallic Rooster (15030544244).jpg|Rooster sculpture, Bordeaux, France. The bird is a symbol of the country.{{cite web |title=Why is France's emblem a rooster? |url=https://www.ensemble-en-france.org/en/rooster-french-symbol/ |website=Ensemble en France |date=September 11, 2019 |access-date=16 March 2025}}

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{{Commons category|Chickens}}

{{Spoken Wikipedia|date=February 22, 2024|Chicken Wikipedia.ogg}}

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