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A rooster (left) and hen (right) perching on a roost

The chicken (Gallus gallus domesticus), a subspecies of the red junglefowl, is a type of domesticated fowl, originally from Asia. Rooster or cock is a term for an adult male bird. A younger male may be called a cockerel; a male that has been castrated is a capon. The adult female bird is called a hen. "Chicken" was originally a term only for an immature, or at least young, bird, but thanks to its usage on restaurant menus has now become the most common term for the subspecies in general, especially in American English. In older sources common fowl or domestic fowl were typically used for this.

Originally raised for cockfighting or for special ceremonies, chickens were not kept for food until the Hellenistic period ( centuries BCE). Humans now keep chickens primarily as a source of food (consuming both their meat and eggs) and as pets.

Chickens are one of the most common and widespread domestic animals, with a total population of 23.7 billion as of 2018 There are numerous cultural references to chickens in myth, folklore and religion, and in language and literature.

of a chicken.

An adult male is a called a cock or rooster (in the United States) and an adult female is called a hen.

young female chicken less than a year old.

In the poultry industry, a pullet is a sexually immature chicken less than 22 weeks of age.

Historically, a chicken was any young domesticated bird, and the species was called domestic fowl or fowl.

Chicken may also mean a chick .mw-parser-output div.crossreference

According to Merriam-Webster, the term "rooster" (i.e. a roosting bird) originated in the mid- or late century as a euphemism to avoid the sexual connotation of the original English "cock", and is widely used throughout North America. "Roosting" is the action of perching aloft to sleep at night, which is done by both sexes.

Anatomy of a chicken.

can be distinguished from the hen by his larger

Diagram of a chicken skull.

Chickens are omnivores.

The average chicken may live for five to ten years, depending on the breed.

Roosters can usually be differentiated from hens by their striking plumage of long flowing tails and shiny, pointed feathers on their necks (hackles) and backs (saddle), which are typically of brighter, bolder colours than those of females of the same breed. However, in some breeds, such as the Sebright chicken, the rooster has only slightly pointed neck feathers, the same colour as the hen's. The identification can be made by looking at the comb, or eventually from the development of spurs on the male's legs (in a few breeds and in certain hybrids, the male and female chicks may be differentiated by colour). Adult chickens have a fleshy crest on their heads called a comb, or cockscomb, and hanging flaps of skin either side under their beaks called wattles. Collectively, these and other fleshy protuberances on the head and throat are called caruncles. Both the adult male and female have wattles and combs, but in most breeds these are more prominent in males. muff or beard is a mutation found in several chicken breeds which causes extra feathering under the chicken's face, giving the appearance of a beard. stic chickens are not capable of long-distance flight, although lighter chickens are generally capable of flying for short distances, such as over fences or into trees (where they would naturally roost). Chickens may occasionally fly briefly to explore their surroundings, but generally do so only to flee perceived danger.

Chickens are gregarious birds and live together in flocks. They have a communal approach to the incubation of eggs and raising of young. Individual chickens in a flock will dominate others, establishing a "pecking order", with dominant individuals having priority for food access and nesting locations. Removing hens or roosters from a flock causes a temporary disruption to this social order until a new pecking order is established. Adding hens, especially younger birds, to an existing flock can lead to fighting and injury. a rooster finds food, he may call other chickens to eat first. He does this by clucking in a high pitch as well as picking up and dropping the food. This behaviour may also be observed in mother hens to call their chicks and encourage them to eat.

A rooster's crowing is a loud and sometimes shrill call and sends a territorial signal to other roosters.

Normal length crowing (with audio).

have a longer crow.

Roosters almost always start crowing before four months of age. Although it is possible for a hen to crow as well, crowing (together with hackles development) is one of the clearest signs of being a rooster.

Rooster crowing contests are a traditional sport in several countries, such as Germany, the Netherlands, Belgium, the United States, Indonesia and Japan. The oldest contests are held with longcrowers. Depending on the breed, either the duration of the crowing or the times the rooster crows within a certain time is measured.

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. and when she responds to his "call", the rooster may mount the hen and proceed with the mating.

More specifically, mating typically involves the following sequence: 1. Male approaching the hen. 2. Male pre-copulatory waltzing. 3. Male waltzing. 4. Female crouching (receptive posture) or stepping aside or running away (if unwilling to copulate). 5. Male mounting. 6. Male treading with both feet on hen's back. 7. Male tail bending (following successful copulation).

Hens will often try to lay in nests that already contain eggs and have been known to move eggs from neighbouring nests into their own. The result of this behaviour is that a flock will use only a few preferred locations, rather than having a different nest for every bird. Hens will often express a preference to lay in the same location. It is not unknown for two (or more) hens to try to share the same nest at the same time. If the nest is small, or one of the hens is particularly determined, this may result in chickens trying to lay on top of each other. There is evidence that individual hens prefer to be either solitary or gregarious nesters.

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Under natural conditions, most birds lay only until a clutch is complete, and they will then incubate all the eggs. Hens are then said to "go broody". The broody hen will stop laying and instead will focus on the incubation of the eggs (a full clutch is usually about 12 eggs). She will "sit" or "set" on the nest, protesting or pecking in defense if disturbed or removed, and she will rarely leave the nest to eat, drink, or dust-bathe. While brooding, the hen maintains the nest at a constant temperature and humidity, as well as turning the eggs regularly during the first part of the incubation. To stimulate broodiness, owners may place several artificial eggs in the nest. To discourage it, they may place the hen in an elevated cage with an open wire floor.

Skull of a three-week-old chicken. Here the opisthotic bone appears in the occipital region, as in the adult Chelonian. bo = Basi-occipital, bt = Basi-temporal, eo = Opisthotic, f = Frontal, fm = Foramen magnum, fo = Fontanella, oc = Occipital condyle, op = Opisthotic, p = Parietal, pf = Post-frontal, sc = Sinus canal in supra-occipital, so = Supra-occpital, sq = Squamosal, 8 = Exit of vagus nerve.

Breeds artificially developed for egg production rarely go broody, and those that do often stop part-way through the incubation. However, other breeds, such as the Cochin, Cornish and Silkie, do regularly go broody, and they make excellent mothers, not only for chicken eggs but also for those of other species even those with much smaller or larger eggs and different incubation periods, such as quail, pheasants, ducks, turkeys, or geese.

Fertile chicken eggs hatch at the end of the incubation period, about 21 days. Development of the chick starts only when incubation begins, so all chicks hatch within a day or two of each other, despite perhaps being laid over a period of two weeks or so. Before hatching, the hen can hear the chicks peeping inside the eggs, and will gently cluck to stimulate them to break out of their shells. The chick begins by "pipping"; pecking a breathing hole with its egg tooth towards the blunt end of the egg, usually on the upper side. The chick then rests for some hours, absorbing the remaining egg yolk and withdrawing the blood supply from the membrane beneath the shell (used earlier for breathing through the shell). The chick then enlarges the hole, gradually turning round as it goes, and eventually severing the blunt end of the shell completely to make a lid. The chick crawls out of the remaining shell, and the wet down dries out in the warmth of the nest.

Hens usually remain on the nest for about two days after the first chick hatches, and during this time the newly hatched chicks feed by absorbing the internal yolk sac. Some breeds sometimes start eating cracked eggs, which can become habitual. Hens fiercely guard their chicks, and brood them when necessary to keep them warm, at first often returning to the nest at night. She leads them to food and water and will call them toward edible items, but seldom feeds them directly. She continues to care for them until they are several weeks old.

Chickens may occasionally gang up on a weak or inexperienced predator. At least one credible report exists of a young fox killed by hens.

Sperm transfer occurs by cloacal contact between the male and female, in a maneuver known as the "cloacal kiss".

Chicken embryos have long been used as model systems to study developing embryos. Large numbers of embryos can be provided by commercial chicken farmers who sell fertilized eggs which can be easily 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 effect later on. For instance, many important discoveries in the area of limb development have been made using chicken embryos, such as the discovery of the apical ectodermal ridge (AER) and the zone of polarizing activity (ZPA) by John W. Saunders.

Given its eminent role in farming, meat production, but also research, the house chicken was the first bird genome to be sequenced.

Populations of chickens from high altitude regions like 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 also has a greater affinity for oxygen, allowing hemoglobin to bind to oxygen more readily.

Male red junglefowl.

Galliformes, the order of bird that chickens belong to, is directly linked to the survival of birds when all other dinosaurs went extinct. Water or ground-dwelling fowl, similar to modern partridges, survived the Cretaceous Paleogene extinction event that killed all tree-dwelling birds and dinosaurs.

The traditional view is that chickens were first domesticated for cockfighting in Asia, Africa, and Europe.

Several controversies still surround the time the chicken was domesticated. Recent molecular evidence obtained from a whole-genome study published in 2020 reveals that the chicken was domesticated 8,000 years ago.

Middle Eastern chicken remains go back to a little earlier than 2000 BC, in Syria; chickens went southward only in the millennium BC. They reached Egypt for purposes of cockfighting about 1400 BC, and became widely bred only in Ptolemaic Egypt (about 300 BC). This change occurred at least 100 years before domestication of chickens spread to Europe.

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.

Domestic chicken in the Americas before Western contact is still an ongoing discussion, 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.

An unusual variety of chicken that has its origins in South America is the Araucana, bred in southern Chile by the Mapuche people. Araucanas, some of which are tailless and some of which have tufts of feathers around their ears, lay blue-green eggs. It has long been suggested that they pre-date the arrival of European chickens brought by the Spanish and are evidence of pre-Columbian trans-Pacific contacts between Asian or Pacific Oceanic peoples, particularly the Polynesians, and South America. In 2007, an international team of researchers reported the results of analysis of chicken bones found on the Arauco Peninsula in south-central Chile. Radiocarbon dating suggested that the chickens were Pre-Columbian, and DNA analysis showed that they were related to prehistoric populations of chickens in Polynesia.

published, apparently pre-Columbian, Chilean specimen and six pre-European Polynesian specimens also cluster with the same European/Indian subcontinental/Southeast Asian sequences, providing no support for a Polynesian introduction of chickens to South America. In contrast, sequences from two archaeological sites on Easter Island group with an uncommon haplogroup from Indonesia, Japan, and China and may represent a genetic signature of an early Polynesian dispersal. Modeling of the potential marine carbon contribution to the Chilean archaeological specimen casts further doubt on claims for pre-Columbian chickens, and definitive proof will require further analyses of ancient DNA sequences and radiocarbon and stable isotope data from archaeological excavations within both Chile and Polynesia.

The debate for and against a Polynesian origin for South American chickens continued with this 2014 paper and subsequent responses in PNAS.

hen, five days after release. Note the pale comb - the comb may be an indicator of health or vigor.

More than 50 billion chickens are reared annually as a source of meat and eggs.

The vast majority of poultry are raised in factory farms. According to the Worldwatch Institute, 74 percent of the world's poultry meat and 68 percent of eggs are produced this way. 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.

A commercial chicken house with open sides raising broiler pullets for meat

Chickens farmed for meat are called broilers. Chickens will naturally live for six or more years, but broiler breeds typically take less than six weeks to reach slaughter size. A free range or organic broiler will usually be slaughtered at about 14 weeks of age.

Chickens farmed primarily for eggs are called layer hens. In total, the UK alone consumes more than 34 million eggs per day.

Keeping chickens as pets became increasingly popular in the

Chickens are social, inquisitive, intelligent Many people feed chickens in part with kitchen food scraps.

A cockfight is a contest held in a ring called a cockpit between two cocks known as gamecocks. This term, denoting a cock kept for game, sport, pastime or entertainment, appears in 1646, Usually wagers are made on the outcome of the match, with the survivor or last bird standing declared winner.

Chickens were originally used for cockfighting, a sport where 2 male chickens or "cocks" fight each other until one dies or becomes badly injured. Cocks possess congenital aggression toward all other cocks to contest with females. Studies suggest that cockfights have existed even up to the Indus Valley Civilisation as a pastime. Today it is commonly associated with religious worship, pastime, and gambling in Asian and some South American countries. While not all fights are to the death, most use metal spurs as a "weapon" attached above or below the chicken's own spur and with this typically results in death in one or both cocks. If chickens are in practice owners place gloves on the spurs to prevent injuries. It has been banned it most western countries and debated by animal rights activist for its brutality.

Many commercial incubators are industrial-sized with shelves holding tens of thousands of eggs at a time, with rotation of the eggs a fully automated process. Home incubators are boxes holding from 6 to 75 eggs; they are usually electrically powered, but in the past some were heated with an oil or paraffin lamp.

Chickens are susceptible to several parasites, including lice, mites, ticks, fleas, and intestinal worms, as well as other diseases. Despite the name, they are not affected by chickenpox, which is generally restricted to humans.

The first pictures of chickens in Europe are found on Corinthian pottery of the century BC.

Chickens were spread by Polynesian seafarers and reached Easter Island in the century AD, where they were the only domestic animal, with the possible exception of the Polynesian rat (Rattus exulans). They were housed in extremely solid chicken coops built from stone, which was first reported as such to Linton Palmer in 1868, who also "expressed his doubts about this".

a type of raffle where the prize is a chicken.