Development Of A Bird Egg

Have you ever wondered about the process of development for a bird's egg? Audubon presents this information by author Jesse Greenspan.

In the week leading up to the laying of a chicken egg, a yolk forms in a mother bird's ovary. It then drops into the oviduct, where it is fertilized by stored sperm.

Next albumen, or egg white, is deposited around the yolk. The shell forms within the following 24 hours, after which the mother pushes the egg out and into the nest.

Chickens have a 21-day incubation period. On day 6 the embryo's heart has been beating for four days; on day 12 beginning bones and feathers are apparent; on day 18 claws and bones look more fully developed, and the embryo is nearly ready to poke its beak into the small air space and inflate its lungs for the first time. On day 21 the chick cracks through the shell with its egg tooth.

Incubation is similar among all bird species, but the length of time varies. Some small songbirds complete their embryonic development in as few as 11 days, while the wandering albatross can take as long as 81 days .

Visit Audubon's magazine site .