February 21, 2007
The Coming Eaglets
We're one week away from our possible hatching date of February 28. In our two previous Eagle Cam seasons, all five of our eaglets arrived on the 35th or 36th day of incubation, so this year we would expect hatching sometime around February 28 or maybe March 1.
If we go too far beyond March 1, then there is the possibility that the first egg was infertile, but we have no reason to believe that this could be the case. Our parents appear to be young and healthy, and that means we expect to see hatching, barring any unforeseen defects with the eaglet itself.
As for the possible hatching hour, we're not sure if the eaglet will first appear in the morning or afternoon, as we've had firstborns arrive at both those times in the past two seasons.
For those who are new to our cam, here is a series of shots showing the first egg hatching in our 2004-2005 season. The camera was closer to the nest that year, so it's easier to see the first small hole in the egg. (Just an FYI: We moved the camera higher the next season so it would be easier to see the eaglets as they grew bigger. Also we raised it because we had problems with the parents hitting the cam with their wings and moving it out of position).
When the eaglet is ready to hatch, it will turn itself inside the egg and pierce the egg's air sac, then it will take its first breath of air from within the shell. Next the chick will use its neck muscles and egg tooth to pip or punch a small hole in the shell. The eaglet will continue to slowly turn and peck until it has cut a hole around the diameter of the shell so that it can push out the bottom half and free itself. This process is very tiring for the chick and can take 24 hours to complete since the young bird will frequently stop to rest. Once the eaglet is out, it will be wet and tired with its eyes closed, but it won't be long before it dries off and is soon able to see and sit up.
Here you can see a photo our first eaglet sitting up for the mother eagle and looking for food, even as its sibling is hatching right beside it.
As for our parents, they will hear the chick chirping and feel it moving inside the shell, so if the incubating parent is frequently moving off the eggs or is looking down at the eggs a lot, that would indicate that they feel or hear something. Biologists believe that eagle parents do not normally assist the eaglet during the hatching process even if the chick is having trouble breaking free.
Once the eaglet arrives, it will not have to be fed right away because before it hatches, it absorbs the yolk and uses that for early nourishment. However, despite the yolk absorption, in the past two seasons our father eagle has been quick to bring fish and even a duck to the nest as soon as hatching was imminent. Perhaps the father eagle gets excited too. :-)
As for the gender of our chicks, in the book The Bald Eagle: Haunts and Habits of a Wilderness Monarch , Canadian eagle biologist Dr. Gary Bortolotti offers evidence of a sex bias based on observations that he collected while studying 37 eaglet broods around Besnard Lake in Saskatchewan, Canada. He reports, "Even though there was an overall nestling sex ratio of one to one, the order in which the sexes hatched was not random; 63% of first-hatched eggs were females, and 68% of second-hatched eggs were males. A sex bias in hatching sequence has only recently been discovered in birds."
Bortolotti speculates that this arrangement might benefit the family because a male eaglet develops faster than a female eaglet, and females being born first would help even out competition in the nest.
Having said that, I can report that in our first Eagle Cam nest -- when we had three eaglets -- our family did not follow this trend. During that year, eagle biologist Craig Koppie -- from the U.S. Fish and Wildlife Service -- climbed our nest tree to remove our middle eaglet for use in the Vermont Bald Eagle Restoration Initiative (to reestablish breeding bald eagles in Vermont). After seeing all three eaglets together in the nest, Craig said he believed that the firstborn eaglet was male and the second female. After the middle chick arrived in Vermont, it was sexed, and they confirmed it was female. (See Craig's photo of our handsome brood).
So our nest was unusual in that the female was born second. Since we had three eaglets that year, it's possible the third eaglet created a different dynamic for our nest as far as gender goes.
By the end of that season, all three of our eaglets fledged successfully due to the wonderful attentiveness of our devoted parents and also due to the abundant food that Blackwater Refuge provided for the large eagle family. We hope we are as fortunate this year with our two-egg nest.
Until next time,
Lisa - webmaster
(contact)