A cloaca is an opening at the end of the digestive tract that serves multiple purposes, such as excreting waste, laying eggs, and transferring sperm. Both male and female chickens have cloacas, but only the male has a small bump inside called the papilla, which is the organ that produces semen.
When chickens mate, the male rooster mounts the female hen and grabs her neck feathers with his beak. He then aligns his cloaca with hers and presses them together for a brief moment. This is called a "cloacal kiss" and it allows the sperm to travel from the rooster's papilla to the hen's oviduct, where it can fertilize her eggs.
Chickens mate for both reproductive and social reasons. Roosters often court hens by offering them food, dancing around them with one wing lowered, or making special sounds. Hens can choose whether to accept or reject a rooster's advances, and they can also store sperm from different roosters for later use. Roosters may also mate with other roosters to establish dominance in the flock.
