The embryos inside the eggs continue the final stages of development. At this point many recognizable structures are in place and the major organ systems are largely formed. There are no highly detailed studies of the embryology of bald eagle eggs - but we can use studies from other raptors, namely American kestrels (Falco sparverius) as a rough guide to what might be happening inside the egg.

By now the feathers of the natal down are in place. The bill has started to harden and scales are covering most of the legs and toes. The eyes are closed and the complexus muscle (hatching muscle) has begun to swell. Much of the remaining amniotic fluid inside the chorioallantois membrane (see archive for egg diagram) has been absorbed. We’ll post again in the coming days with more of what’s happening inside the eggs as they get closer to hatching.

This information is based on:
Pisenti JM, Santolo GM, Yamamoto JT, Morzenti AA. 2001. Embryonic Development of the American Kestrel (Falco sparverius) External Criteria for Staging. J Raptor Res. 35(3):194-206

Labels: bald eagle, eggs, hatching