January 31, 2007
Eagle Cam Video
In this web log entry, we're offering three video clips that were captured last Saturday from the Eagle Cam monitor at the Blackwater Refuge Visitor Center. If you ever pay a visit to the Refuge, be sure to drop by our Visitor Center where you can watch the Osprey Cam and Eagle Cam video live on our TV monitors.
Before we talk about the video clips, it might be a good idea to talk a little about the incubation process, which is what we're seeing in the video. Incubation is the process of applying heat to the egg so the embryo inside will develop and hatch. Our eggs are about a week old, and already the eaglets are growing body parts inside their shells. This Embryonic Development Chart shows how a chicken egg develops during the chick's 21-day incubation period. The chicken's incubation period is two weeks shorter than the eaglet's, but all the general body parts are there.
Both our eagle parents have a brood patch -- a featherless area on their breasts that is infused with blood vessels and sensitive to temperature -- and both adults will incubate, although the female will do it the majority of the time.
As far as the parents' relationship, the female is the dominant bird by virtue of her larger size -- she's about one-third larger than the male (same as ospreys). Biologists speculate that the reason the females are larger is because they spend more time protecting the eggs and chicks when they're most vulnerable, while the males spend more time hunting for food and chasing off intruders, and thus the males are required to be quick and agile.
Video Clips
Our three video clips are for the Windows Media Player. Right-click on the images below and choose "Save Target As" or "Save Link As" to download the movies to your hard drive. Note that there is no audio with the clips as we do not have a microphone mounted on the tree.
In our first video clip we see a funny little exchange between our two devoted parents. The female eagle flies in with a piece of the always-popular pine spray and proceeds to place it on the male's back, while he's lying in the nest incubating the eggs. (Note: She did this on Friday, as well).
We can't be sure if mom was trying to tell dad that he needs freshening up or if she was dropping a subtle hint that she wanted to take over incubation, but the male takes the pine branch off his back only to have the female put it right back on him. This time the male indulges the female and leaves the branch alone but doesn't get up from his comfortable spot on the eggs, so the female flies off to look for more pine sprays. After the female is out of sight, the male removes the pine for good.
In the second clip we get a good view of how the eagle parent incubates the eggs. The male gets up and begins to roll the eggs around a bit and also aerates the grass that is beneath the eggs. Next the male lies down over the eggs, hooks his sharp beak into the nest to anchor himself, and then rocks back and forth over the eggs until they're nice and tight against his brood patch. After the eggs are in position, he pulls in the surrounding grasses so they are closer to his body.
If you watch the Eagle Cam monitor at our Visitor Center for a long time, you see that the parents spend a lot of time fussing with the sticks and grasses around them until they're finally satisfied with the arrangement.
In the final clip we see a nice example of an incubation switch. The female comes in with another pine spray, and this time looks like she wants to put it on the male's head, so he gets up. After the male flies away to stretch his wings and maybe eat, the female settles in over the eggs, showing the same hooking/rocking behavior that we saw in the male. Finally she pulls the grasses closer to her body.
In order to illustrate how the parents differ in size, here are two screen grabs from the clips that show how the female is noticeably bigger and longer.
In the next few web log entries we'll talk more about the parents' relationship and more about the eggs -- such as the possible gender of the chicks.
Also, for those just joining us, be sure to download our Eagle Watchers' Guide (2.5 MB PDF file) to see a recap of our first Eagle Cam season and to learn interesting facts about eagles and their young.
Until next time,
Lisa - webmaster
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