As of this blog post, DNF’s two eggs are 28 and 25 days old, Mrs. T’s three eggs are eight, five, and two days old, and Ma FSV’s four eggs are 18, 14, 11, and 7 days old. Hatch watch for Decorah North begins on March 19.
What do embryonic eagles look they look like as they develop and grow inside their eggs? Dr. Peter Sharpe from the Institute for Wildlife Studies developed a table of bald eagle embryonic development based on work done by Hamburger and Hamilton (1951). While this animation uses a chicken instead of a bald eagle, the sequence of development is fairly similar.
Development of an avian embryo
What happened between the 17th and 24th day? When we last peeked inside the egg, our embryonic eagle had a beak tipped with a sharp egg tooth, long bent limbs, feather germs, and eyelids. Although it had a lot of growing and development to do, a bird was clearly taking shape.
Day 17 to Day 24
Between day seventeen and day twenty-four, our eaglet grew from roughly .7 inches in size to 1.1 inches in size. Its developing digits differentiated into toes and wing bones, it sprouted dermal appendages like down, scales, talons, and plantar footpads, and its eyelids closed. While it still has a lot of growing left, our embryonic eaglet looks like a bird.
At this point, we are about 65% of the way to hatch and most of the embryo’s major morphological changes are behind it. Its eyelids will close as its eyes settle into their sockets, its down will grow longer, and it will put on muscle and tissue as it swells to its hatching weight of 2.5 to 3.5 ounces. While I couldn’t find any authoritative sources on hatchling body length, the size of the egg suggests the hatchling will be just under three inches long. Now that most of the embryo’s systems are in place, it’s time to grow!
Curious about hatch? Watch this 2023 video showing hatch in Decorah and look for a blog when hatch watch starts!
Image Credit
Things that helped me learn about this subject:
The Raptor Resource Project