Chicken Types, Characteristics & Uses

Although many taxonomists and ornithologists consider it as a domesticated form of the wild red jungle fowl, some classify it as a subspecies of the red jungle fowl (i.e., G. gallus domesticus), whereas others, including the U.S. Chicken, (Gallus gallus), any of more than 60 breeds of medium-sized poultry that are primarily descended from the wild red jungle fowl (Gallus gallus, family Phasianidae, order Galliformes) of India. In the UK and Europe, laying hens are then slaughtered and used in processed foods, or sold as ‘soup hens’. Hens of some breeds can produce over 300 eggs per year; the highest authenticated rate of egg-laying is 371 eggs in 364 days. During the Hellenistic period (4th–2nd centuries BC), in the southern Levant, chickens began to be widely domesticated for food.

Reproduction and life-cycle

Chickens have been thought of primarily as providers of food, but their cognition, emotions, and sociality are comparable with other birds and mammals. Chickens are gregarious, living in flocks, and incubate eggs and raise young communally. The body is round, the legs are unfeathered in most breeds, and the wings are short. Chicken can mean a chick, and this was historically the meaning of the word chicken, as in William Shakespeare’s play Macbeth, where Macduff laments the death of «all my pretty chickens and their dam». As of 2023, the global chicken population exceeds 26.5 billion, with more than 50 billion birds produced annually for consumption. It was first domesticated around 8,000 years ago and is one of the most common and widespread domesticated animals in the world.

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. Large numbers of embryos can be provided commercially; fertilized eggs can easily be opened and used to observe the developing embryo. Keeping chickens as pets became increasingly popular in the 2000s among urban and suburban residents.

• Individual chickens dominate others, establishing a pecking order; dominant individuals take priority for access to food and nest sites.
• Only in the early 20th century, however, did chicken meat and eggs become mass-production commodities.
• An early study proposed that a single domestication event of the red junglefowl in present-day Thailand gave rise to the modern chicken.
• A flock usually includes one dominant adult male, a few subdominant males, and two or more females that are carefully watched over by the dominant male.
• Despite the chicken’s close relationship with the red jungle fowl, there is evidence that the gray jungle fowl (G. sonneratii) of southern India and other jungle fowl species, also members of Gallus, may have contributed to the bird’s ancestry.

Reproduction and life-cycle

Genomic studies estimated 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. 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. The concept of dominance, involving pecking, was described in female chickens by Thorleif Schjelderup-Ebbe in 1921 as the «pecking order». Individual chickens dominate others, establishing a pecking order; dominant individuals take priority for access to food and nest sites.

Domestication and economic production

Under natural conditions, most birds lay only until a clutch is complete; they then incubate all the eggs. 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. In older sources, and still often in trade and scientific contexts, chickens as a species are described as common fowl or domestic fowl. Many immature males (cockerels) are castrated (usually chemically, with hormones that cause atrophying of the testicles) to become meat birds (capons).

Despite the chicken’s close relationship with the red jungle fowl, there is evidence that the gray jungle fowl (G. sonneratii) of southern India and other jungle fowl species, also members of Gallus, may have contributed to the bird’s ancestry. The chicken is a sacred animal in many cultures and deeply embedded in belief systems and religious practices.Roosters are sometimes used for divination, a practice called alectryomancy. This stimulates the hen to lose her feathers but also re-invigorates egg-production. In some other countries, flocks are sometimes force-moulted rather than being slaughtered to re-invigorate egg-laying.

The market eaub.info/ for chicken meat has grown dramatically since then, with worldwide exports reaching nearly 12.5 million metric tons (about 13.8 million tons) by the early 21st century. By the mid-20th century, however, meat production had outstripped egg production as a specialized industry. For most of that period, chickens were a common part of the livestock complement of farms and ranches throughout Eurasia and Africa. Chicken domestication likely occurred more than once in Southeast Asia and possibly India over the most recent 7,400 years, and the first domestications may have been for religious reasons or for the raising of fighting birds. Each flock of chickens develops a social hierarchy that determines access to food, nesting sites, mates, and other resources. At about six months, males produce viable sperm, and females produce viable eggs.