Hatch Watch begins at Trempealeau today! Mrs. T’s first egg will turn 36 days old and, while her first egg usually hatches at about the 39-day mark, hatch is a process: the third great landmark in the life of a chick. Watch live here: https://www.raptorresource.org/trempealeau-eagles/.
A fully developed embryo lies scrunched up inside the egg, with its ankles at the pointed end and its head at the blunt end. Its neck is bent so that its head lies with its beak poking out beneath the right wing, up against the egg membrane.
Internal Pip
Before hatching, the eaglet must shift from relying on membranes and external blood vessels for oxygen and nutrients to breathing with its lungs and digesting with its gastrointestinal system. It shuts off blood flow to the vessels lining the shell’s inner surface, absorbs the remaining yolk into its abdomen, and uses its egg tooth to puncture the air cell at the blunt end of the egg. Although the shell has thinned as calcium was drawn for skeletal development, it remains a formidable barrier, and the oxygen diffusing through the shell is no longer enough to meet the hatchling’s respiratory needs. Taking a breath from the air cell – big gulp now! – gives it the oxygen and energy it needs to break through the shell. We can’t see a pip yet, but hatch has started!
External Pip
As the eaglet breaks through the outer shell, it takes its first breath of air outside the egg. Fans around the world take a deep breath and begin pacing the delivery room floor, while the hatchling, energized by the pulse of extra oxygen and encouraged by its parents’ soft chirps, pushes its legs against the bottom of the shell to gain leverage and begins to rotate counter-clockwise, cutting its way through the shell as it goes.
Our eaglets generally arrive 24-36 hours after we notice the first starring on the blunt end of the eggshell, although hatch can take considerably longer than that. Watch with us as we cross our fingers, toes, and talons, and wait for TE3, TE4, and TE5 to break free!
The term ‘pipping’—when the chick first breaks through the shell—may have originally been called ‘peeping’ after the sound the chick makes at this stage. In The Most Perfect Thing: Inside (and Outside) a Bird’s Egg, Tim Birkhead notes a 1621 account by Fabricius titled ‘Peeping is a sign that the chick wishes to leave the egg’. Listen to and watch a previous hatch video here to get ready! https://youtu.be/yHUkArhtL8o?si=KUHvDSeJzuW1-QKS.
Hatching is hard work!
The Raptor Resource Project