Chicken

Gallus gallus domesticus

The chicken (Gallus gallus domesticus) is a type of domesticated fowl, a subspecies of the red junglefowl (Gallus gallus). They are one of the most common and widespread domestic animals, with a total population of more than 19 billion as of 2011. There are more chickens in the world than any other bird or domesticated fowl. Humans keep chickens primarily as a source of food (consuming both their meat and eggs) and, less commonly, as pets. Chickens are social 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.

In the UK and Ireland, adult male chickens over the age of one year are primarily known as cocks, whereas in the United States, Canada, Australia and New Zealand, they are more commonly called roosters. Males less than a year old are cockerels. Females over a year old are known as hens, and younger females as pullets. Chickens are omnivores. In the wild, they often scratch at the soil to search for seeds, insects and even animals as large as lizards, small snakes or young mice. 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.