CHICKEN中文繁體翻譯：劍橋詞典

Chickens are common and widespread domestic animals, with a total population of 23.7 billion as of 2018update. The first pictures of chickens in Europe are found on Corinthian pottery of the 7th century BC. Phoenicians spread chickens along the Mediterranean coasts as far as Iberia.

It was first domesticated around 8,000 years ago and is one of the most common and widespread domesticated animals in the world. The life span of a chicken varies between 5 – 7 years although there have been cases of chickens living 20 years or so. During this time, the newly-hatched chicks live off the egg yolk they absorb just before hatching.

Are Chickenss endangered?

Chickens are social animals with complex vocalizations and behaviors, and feature in folklore, religion, and literature across many societies.

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Genetic sequencing of chicken bones from archaeological sites in Europe revealed that in the High Middle Ages chickens became less aggressive and began to lay eggs earlier in the breeding season. The possibility that domestic chickens were in the Americas before Western contact is debated by researchers, but blue-egged chickens, found only in the Americas and Asia, suggest an Asian origin for early American chickens. Analysis of the most popular commercial breed shows that the White Leghorn breed possesses a mosaic of divergent ancestries inherited from different subspecies of red junglefowl. Archaeological evidence appeared to support domestic chickens in Southeast Asia well before 6000 BC, China by 6000 BC and India by 2000 BC. Exactly when and where the chicken was domesticated was controversial. Inbreeding of White Leghorn chickens tends to cause inbreeding depression expressed as reduced egg number and delayed sexual maturity.

Hens remain on the nest for about two days after the first chick hatches; during this time the newly hatched chicks feed by absorbing the internal yolk sac. The hen sits on the nest, fluffing up or pecking defensively if disturbed. Reproduction declines with age, thought to be due to a decline in GnRH-I-N. 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.

• The life span of a chicken varies between 5 – 7 years although there have been cases of chickens living 20 years or so.
• Hens of some breeds can produce over 300 eggs per year; the highest authenticated rate of egg-laying is 371 eggs in 364 days.
• 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 domestic chicken has subsequently hybridised with grey junglefowl, Sri Lankan junglefowl and green junglefowl; a gene for yellow skin, for instance, was incorporated into domestic birds from the grey junglefowl (G. sonneratii).

When eggs are placed in a hypoxic khelovip live environment, chicken embryos from these populations express much more hemoglobin than embryos from other chicken populations. In older sources, and still often in trade and scientific contexts, chickens as a species are described as common fowl or domestic fowl. Besides humans, lots of animals eat chickens as well. Modern egg-laying breeds rarely go broody and those that do often stop part-way through the incubation cycle.

A flock thus uses only a few preferred locations, rather than having a different nest for every bird. Hens often try to lay in nests that already contain eggs and sometimes move eggs from neighbouring nests into their own. The concept of dominance, involving pecking, was described in female chickens by Thorleif Schjelderup-Ebbe in 1921 as the “pecking order”. Chickens are gregarious, living in flocks, and incubate eggs and raise young communally. 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 domesticating the chicken, humans took advantage of the red junglefowl’s ability to reproduce prolifically when exposed to a surge in its food supply. The chicken (Gallus gallus domesticus) is a domesticated form of the red junglefowl (Gallus gallus), originally native to Southeast Asia. Females (mature hens and younger chickens, called pullets) are raised for meat and for their edible eggs. The chicken is perhaps the most widely domesticated fowl, raised worldwide for its meat and eggs. These domesticated chickens spread across Southeast and South Asia where they interbred with local wild species of junglefowl, forming genetically and geographically distinct groups.