The wet feathers help cool the eggs and keep them at the proper temperature. Still others like the house wren simply adjust the amount of time they sit on the eggs according to the temperature of the air. On very warm days, they sit for seven or eight minutes at a time. On cooler days they will sit for 14 or 15 minutes at a time. In this way they control the temperature of the eggs.
Birds also turn their eggs with their beaks during incubation.
By turning the eggs, birds can apply heat more evenly to the eggs. The incubating of the eggs varies from species to species. In most species the female does the incubating but in some species the incubating is shared between the male and female. The male rose-breasted grosbeak shares incubating duties with the female. In some species the female does all the incubating and the male brings her food.