CHICKEN BIRD

Chickens ,(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. The chicken is perhaps the most widely domesticated fowl, raised worldwide for its meat and Eggs.

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. There is some debate about what the chicken’s scientific name should be. 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 US Department of Agriculture , classify the bird as G. domesticus.

Natural history 

Chickens have a squat and rounded appearance. They stand less than 70 cm (27.6 inches) tall and weigh approximately 2.6 kg (5.7 pounds) on average. Males (called cocks or roosters ) and females (hens) are known for their fleshy combs, lobed wattles hanging below the bill, and high-arched tails. In some roosters, the tail can extend more than 30 cm (12 inches) in length.

Chickens breed in the spring and summer months. Egg laying is stimulated by the long stretches of daylight that occur during the warmer months; however, artificial lights placed in chicken coops can trigger a hen’s egg laying response throughout the year. The time between Ovulation and egg-laying is approximately 23–26 hours. Subsequent ovulations may occur within an hour after the previous egg was laid, allowing some hens to produce as many as 300 eggs per year.

Fertilized embryos develop quickly, and chicks hatch approximately 21 days later. Chicks are born covered in down, but they mature quickly, becoming fully feathered after four to five weeks. At about six months, males produce viable Sperm and females produce viable eggs. Members of free-ranging flocks may live for six to eight years under the best conditions, but most chickens used in the poultry industry serve as egg layers for two to three years before being slaughtered for their meat, with much of it being used in pet food.Chickens in captivity have been known to live for up to 30 years.

Social Hierarchy 

Each flock of chickens develops a social hierarchy that determines access to food, nesting sites, mates, and other resources. 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. Social hierarchies in chickens are segregated by sex and manifest as a pecking order , in which individuals of higher social rank may strike out at individuals of lower rank with their beaks (pecking) to ensure access to food and other resources. Altercations, however, may also include pummeling with wings and scratching with claws

Chickens belonging to the same age cohort and sex are often kept together in industrial production settings. The pecking order is established within groups of female chicks by the 10th week of life. In groups of male chicks, however, fights for dominance may continue into adulthood. In situations where one adult bird challenges another—which happens most often when a new bird is introduced into the flock—fights involving males risk injury and death more often than fights involving females.