Birds keep their eggs warm by sitting on them for days or weeks.

The longer version

Incubation holds the embryo near a narrow temperature band. Too cold and development stalls; too hot and proteins stop working properly. The parent presses a bare patch of skin against the eggs, an area known as the brood patch, which loses its feathers and grows extra blood vessels to pass heat on efficiently.

Eggs are turned regularly so the embryo does not stick to the shell membrane and so warmth spreads evenly. Parents also manage humidity and shade the clutch in hot sun. Some species begin incubation with the first egg, so chicks hatch days apart, while others wait until the clutch is complete so all hatch together.

Where this entry sits

Here you will find feathered trivia about flight, migration, nests, eggs, and the songs birds sing. Expect short surprising facts on penguins, owls, hummingbirds, and other familiar birds from gardens, forests, wetlands, and distant coastlines. The full list sits on the Birds page, where every entry is listed in order.