In nature, the female bird selects the nest site and lays a clutch of eggs (usually 8 to 13 eggs), one egg per day. Once she has a clutch of eggs, she begins sitting on the eggs full time, leaving only for food and water.

The hen's body temperature is 105° F to 106° F. When the hen sits on the eggs, she heats the eggs to 100° F to 101° F. The hen turns the eggs on a regular basis by using her beak to scoop under the egg and roll it toward her. The humidity comes from the environment, the hen's body, and any moisture she transfers back to the nest on her feathers. Brooding hens often leave their nests to feed at dawn or dusk when the dew is present on the grass.