About 22 million chickens are consumed in the United States each day. The chicken is among the most plentiful of domesticated animals, and there are more chickens than any other bird in the world as of 2014.
Chickens and chicken eggs are food sources for humans. About 50 billion chicken eggs are produced annually in the United States. Chickens used for producing eggs are known as layers. Male chickens over a year old are roosters, and cockerels are males less than a year old. Females more than a year old are hens, and females not yet a year old are known as pullets. In egg farming, pullets are known as hens when they begin laying eggs, typically by 20 weeks old.