For the culinary use chicken recipes easy and quick chickens, see Chicken as food. Male and female chicken sitting together.

Chickens are one of the most common and widespread domestic animals, with a total population of 23. 7 billion as of 2018, up from more than 19 billion in 2011. In 2011 a study in genetic and archaeological evidence conclude that the origin of the modern-day chicken is from Southeast Asia. Dunghill fowl: a chicken with mixed parentage from different domestic varieties. Pullet: a 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.

In fact, chicken was originally a term only for an immature, or at least young, bird. In older sources, chicken as a species were typically referred to as common fowl or domestic fowl. Chick is then rarely used to mean chicken, but is mainly used in Merriam-Webster’s “Sense 1b” viz. This section needs expansion with: the origin of the term ‘chicken’ in general. You can help by adding to it. In most breeds the adult rooster can be distinguished from the hen by his larger comb. In the wild, they often scratch at the soil to search for seeds, insects, and even animals as large as lizards, small snakes, or sometimes young mice.

10 years, depending on the breed. The world’s oldest known chicken lived 16 years according to Guinness World Records. However, in some breeds, such as the Sebright chicken, the rooster has only slightly pointed neck feathers, the same colour as the hen’s. 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. When 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. However, roosters may also crow in response to sudden disturbances within their surroundings.

Hens cluck loudly after laying an egg, and also to call their chicks. Chickens also give different warning calls when they sense a predator approaching from the air or on the ground. For the nursery rhyme, see Cock a doodle doo. Long-crowing chickens have a longer crow. Roosters almost always start crowing before four months of age.

Rooster crowing contests, also known as 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. 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. 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. This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. 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”.

Here the opisthotic bone appears in the occipital region, as in the adult Chelonian. Breeds artificially developed for egg production rarely go broody, and those that do often stop part-way through the incubation. 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. 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. Chickens may occasionally gang up on a weak or inexperienced predator. At least one credible report exists of a young fox killed by hens. A group of hens have been recorded in attacking a hawk that had entered their coop. If a chicken is threatened by predators, stress, or is sick, there is a chance that they will puff up their feathers. 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 organisms 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. In 2006, scientists researching the ancestry of birds “turned on” a chicken recessive gene, talpid2, and found that the embryo jaws initiated formation of teeth, like those found in ancient bird fossils. John Fallon, the overseer of the project, stated that chickens have “retained the ability to make teeth, under certain conditions . Chicks atop a picture of a genetic map of a chicken. Given its eminent role in farming, meat production, but also research, the house chicken was the first bird genome to be sequenced.