Chicken

Description

They are midsize birds with a characteristic crest on the head. They have evident sexual dimorphism: the males are much larger and their crests are redder and more upright, with spurs and abundant and curved tail feathers as symbols of dominance; those of the females are smaller and with less striking colours. 

Ethology

They are territorial and inside the henhouse they have a very marked hierarchy, especially if there are males. The females lay 1 egg a day that is not fertile, unless she has mated with the male beforehand. In the mating season, the cock “mounts” the female to copulate, and may leave her immobilised for up to 30 minutes. When the females have a calcium deficit, they may pluck at the eggs to get the calcium from the shell. 

Interesting facts

Selection by humans has resulted in chickens losing the ability to fly. The cocks will often crow loudly at daybreak, but they normally sing all day as a symbol of dominance to the rest of the group.