I decided to hold off posting a new blog entry until I was sure all the eggs had arrived. As it stands, we have two very healthy-looking eggs in the nest, and we’re very pleased with the amount. Two eggs is a normal clutch size and the extra egg gives us insurance in case one of the eggs doesn’t hatch — although there’s no reason to think that both won’t hatch.

Here is our 2008 egg scorecard:

1st egg
Laid: January 26
Possible Hatch: March 1 or 2

2nd egg
Laid: January 30
Possible Hatch: March 5 or 6

Paula, who is one our regular cam watchers, has posted a video on YouTube showing the moments when our first egg was laid. Be sure to check out her movie, and much thanks to Paula for sharing this.

Although bald eagle eggs can hatch anywhere in the 32-36 day range, the eggs we have had in previous years have normally hatched on the 35th or 36th day, so that is how I calculated the hatch dates.

As past readers of the Blackwater blogs know, we often pay attention to how much time there is between the laying of each egg because it will determine how far ahead the oldest chick will be in development. Our youngest egg was over three days behind the oldest egg, so we kind of hope the youngest chick hatches at the early part of its date range, so it isn’t too much smaller than the oldest chick. If the size difference is large, it can increase the chances of bullying by the oldest chick.

I wanted to post some of the egg information that I know a lot of our cam watchers are wondering about. First regarding the size of the eggs: According to the Journey North website:

“The eggs are dull white in coloration and may appear with some darkish flecks or staining. The surface of the shell is rough when compared to a chicken egg and the overall shape is rounder when compared to many bird species. On average, an eagle egg will measure 2.75 inches long by 2.25 inches wide, surprisingly small for a bird that will grow to have a six and half foot wingspan and weigh between 10 and 14 pounds before it leaves the nest in July.”

Once they arrive, newborn bald eaglets are about 4-5 inches in length, and weigh about 70-105 grams at birth, but will gain up to 180 grams a day. In fact, it’s been stated that bald eaglets are the fastest growing birds in North America. So our eggs may start out small, but once the chicks arrive, they will grow very fast.

Both parents have a brood patch, which is a featherless area on their breasts that is infused with blood vessels and is sensitive to temperature, and they place the patch against the eggs to keep them warm. (It’s helpful to think of the brood patch as a hot-water bottle resting against the eggs.) In addition to using the brood patch to keep the eggs warm, the parents also use the nest cup to keep the eggs protected from the elements, and you might have noticed how the nest cup actually has walls to keep in the warmth. Our eagle parents take turns incubating the eggs, although the mother does it more often, and the parents also turn the eggs about once an hour to ensure that the embryo does not stick to the inside of the shell.

If the parents do a good job of keeping the eggs warm and turning them in a timely manner, then the cells inside the egg will begin to turn into healthy organs, wings, a beak, a tail, etc. However, there are times when eggs don’t hatch, and there can be several reasons for this, such as the egg was infertile, the parents had a poor diet or were exposed to pesticides, the eggs were not turned often enough, the eggs were not kept warm enough, or the membranes and tissues inside did not develop properly.

I know some cam watchers are concerned when they see the eggs uncovered, but keep in mind that the parents are the best judges as to how warm the eggs are at any given moment and how long they can be left uncovered. Also, when it looks like the eggs are alone, it’s important to remember that just because we can’t see the eagles does not mean they are not nearby. In fact, an adult eagle could be sitting in the branches just above the cam watching the eggs the entire time.

Some folks have also asked about us centering the cam now that the female has chosen to have the nest cup toward the back of the nest. Legally we cannot disturb the eagles until the chicks are about a month old, so the cam that sits up in the tree is off limits to us until that time. We have noticed that the camera has moved a bit to the left, and we think that was caused by the eagles bumping the cam box while flying in and out. We’re hoping it doesn’t move much more, since our view is still good, but that is part of the gamble with an Eagle Cam — once you put the equipment 80-feet up in a tree with a protected (and often human-sensitive) species, you can’t risk disturbing the birds once eggs or small chicks are in the nest. So we’ll just keep our fingers crossed that our good view holds for the next couple months.

And last but not least, I wanted to point out a photo that shows a position a couple cam watchers had wondered about. In this shot from the cam, we see the adult using its preen gland. The eagles have a preen gland — or oil gland — at the base of their tails. They remove oil from the gland and put it on their feathers to clean them and waterproof them. Even if the adult is spending a lot of time on the nest, it still needs to waterproof its feathers to protect it from snow and rain. So when you see the eagle in this position, it’s often removing oil from its gland and spreading it on its feathers.

Norfolk Cam

I also wanted to briefly mention the Eagle Cam in Norfolk, Virginia because they posted some interesting shots the other night of a Great horned owl visiting the eagle nest. In fact, the owl didn’t just visit — it sat down in the nest for a while and made itself at home, and later tried to attack the female while she was laying the first egg. Check out this video on YouTube which shows the attack.

Great horned owls have been known to take over eagle nests, and they can also be predators of raptor chicks (and sometimes even raptor adults, like ospreys). But while it seems unlikely the owl could ever harm a full-grown female bald eagle, it could definitely cause enough trouble to interfere with proper nesting and incubation of the first egg. Hopefully the eagle parents will be able to persuade the owl to stay away.

Woody Dawson

Finally, I wanted to mention some good news related to our friend Woody Dawson. Woody is a wonderful photographer who photographs eagles along the Susquehanna River in northern Maryland and also in Alaska, and I’ve occasionally shared his work in my blogs. Woody just notified me that six of his photos were just used in a brochure put out by the U.S. Mint for their new bald eagle commemorative coin series. Here are two images showing the brochure: Image one and Image two. The only photo that is not Woody’s is the image on the far right on the first brochure — that is a photo of Challenger, the captive bald eagle from the American Eagle Foundation. Right now, these are the only copies we have of the brochure, but we wanted to share them, and we wanted to congratulate Woody on this wonderful honor. If you’d like to see more of Woody’s work, be sure to visit his website.

Technical Note
One closing technical note: We’ve noticed that our cam pages have been a bit sluggish lately, even failing to load sometimes. I’ve notified our ISP and we’re looking into the issue, which is likely being caused by our web server. We’ll try to get it cleared up before we get close to hatching time. Thanks for your patience.

Until next time,
Lisa - webmaster
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eagles, wildlife refuge, eagle cam, eagle eggs, Blackwater Refuge, Maryland