February 04, 2007

Immature Bald Eagles

First thing I wanted to do was answer a question from a cam watcher who wrote in but forgot to supply their email address. They asked if the eagle nest was man-made and how high the nest is in the tree. The nest is a natural nest made by the eagles themselves in a loblolly pine tree. The nest sits about 80 feet off the ground, and our camera is about six feet above the nest. We have to use the services of a professional tree climber to get up there and work on the camera whenever it requires maintenance.


Immature Bald Eagles

In the last week or so, we've seen an immature bald eagle hanging out around the osprey platform -- sometimes by itself and sometimes with an adult. Cam watchers have been asking several questions about the immature eagle, so I thought it would be a good time to talk more about them.

Many folks are surprised to learn that a bald eagle does not have a white head and tail when it gets its first set of feathers. In fact, the young eagle will not achieve the look of the adult until it's four to five years old, which is when it will reach breeding age. Below are a set of photos that show the major stages in the appearance of a bald eagle. Click on the thumbnails below for a larger image:

eaglesr1 eaglesr2
eaglesr3 eaglesr4
eaglesr5 eaglesr6

In photo #1 we see two eaglets with their first coat of down right after their birth (note the egg tooth on the tip of their beak -- they use it to break out of the shell, then it falls off several weeks later). In photo #2 we see an eaglet with its woollier second coat of down. In photo #3 we see an eaglet with the first set of dark feathers coming in and pushing out the down. In photo #4 we see one of the Maryland eaglets that was relocated to Vermont -- this bird was very close to fledging and had most of its first feathers. In photo #5 we see a sub-adult eagle that is beginning to get its all-white head but still has an eye-stripe and mottled coloring on its body. And in photo #6 we see an adult bald eagle with the distinctive all-white head and tail, and all-brown body.

As immature eagles go through the various brown/white stages, they can possess a wide variety of mottled coloring on their feathers, and two birds the same age might not even look exactly the same. Also, immature bald eagles are often mistaken for golden eagles from a distance because of the brown coloring on their heads and tails.

As for the immature bald eagle on the osprey platform, he looks to be between two to three years old. According to our photographer friend Bob Quinn -- who recently took this photo of the immature chasing the adult near the platform -- it appears that at times the eagles are competing with one another, yet we've also seen them on the platform together, so it looks like they might tolerate each other on occasion.

The immature is as big as the adult -- in fact he may be bigger since immatures have longer feathers -- so the adult does not have a size advantage unless they are of a different sex. Immatures and adults will sometimes hang out near each other if they are feeding from the same source (like a carcass or a group of dead fish) but things will turn hostile if one of them tries to steal the others food, which might happen, especially if the immature eagle is having trouble finding his own food due to his inexperience as a hunter.

You can see an aerial food battle in action at this amazing gallery by photographer Stan Bousson, which features a series of shots showing an immature bald eagle stealing a meal from the adult. Based on the photos, it looks like the eagles may have been cartwheeling at some point during the battle.

Winter is a hard time for immature eagles. Many of those that die their first year will die because of starvation. Just because they can fly does not mean that they have mastered the art of catching or finding their own food. Becoming an efficient hunter is perhaps the hardest skill of all to master.


Wanderers

olderimmature.jpgImmature eagles spend the first few years of their lives wandering, sometimes over great distances. So there is a possibility that the immature bald eagle on the osprey platform was not born at Blackwater but is visiting from states north of Maryland or even from Canada. Once an immature eagle is about to reach breeding age, it will normally return to the area where it was born and begin looking for a mate and a nesting site.

Biologists have speculated that the reason immature eagles have different coloring is so adults will not see them as a threat to their mate or their nesting site. If the young birds looked just like the adults, but were not of breeding age yet, they would find life much more difficult as the adults might see them as a threat and attack them.

Immature bald eagles will sometimes sit together in the trees at Blackwater Refuge -- maybe they find solidarity in being in the company of other young eagles or maybe they have a better chance of finding food if they hang around other eagles that are looking for an easy meal.

In this photo by Bob Quinn, you can see five immature bald eagles sitting in a group of loblolly pine trees together at the Refuge. Note that the one young eagle with the whitish head appears to be the oldest, although it looks like he still has some brown coloring on his head so he probably hasn't reached breeding age yet. Much thanks again to Bob for sharing his Refuge photography with us.

We'll update the Eagle Cam Gallery later this week.

Until next time,
Lisa - webmaster
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Posted by Webmaster at February 4, 2007 03:47 PM