January 09, 2007
The Eagles' Eyrie
We have several visual offerings this week. If you didn't see the link on the Osprey Cam page, we have posted a beautiful Blackwater fall migration video from Georgena Terry, who is the founder of Terry Precision Cycling. Georgena is a generous supporter of Blackwater Refuge, and we thank her for sharing her video and talents with us. To view the 7MB video, right-click on the link and choose "Save Target As" to download:
Also, local photographer Bob Quinn has posted some great new photos of Blackwater's adult and immature bald eagles (newest photos are at the bottom of the page). Much thanks to Bob for sharing these wonderful shots with us.
Finally, an immature bald eagle made a brief showing at the Osprey Cam nest on Tuesday.
The Eagles' Eyrie
In previous entries of our Eagle Cam Web Logs, I've often referred to the eagles' nest as just that -- a "nest." But many writers and biologists also refer to the eagles' nest as an "eyrie." The word "eyrie" refers to any lofty nest of a bird of prey, and it is frequently used when discussing the home of the eagle -- perhaps because it sounds more majestic than simply saying "nest."
Eagles have a very strong bond to their nest or eyrie. In fact, some biologists have speculated that the ties to the home eyrie are even stronger than the ties to a particular life mate.
If an eagle loses a partner, they will often quickly find another, and take them back to the old nest. In addition, eagles that migrate will separate at migration time, but when they return, will come back to the home nest as if it is a beacon -- even if the other partner is not coming back due to death or injury.
And when the nest is blown down or the tree holding the nest crashes to the ground, the eagles will often rebuild in the same area, frequently using materials from their fallen home. Some biologists even speculate that the act of building the nest together is even more crucial to the couple's bonding than cartwheeling or sky dancing together.
So the importance of the eyrie cannot be overstated, because for the eagles their nest is a migration destination, a perching platform, a bedroom, a dining room, and also a crib and exercise room for the little eaglets. In all ways, it is truly a home.
Eagle Cam Nest
At our Eagle Cam tree, the couple has built their home in a lofty, living loblolly pine tree, which is the species most favored by nesting bald eagles around the middle and lower Chesapeake Bay. The nest is about 80 feet from the ground and appears to be an average-sized structure. We don't know how old the nest is, but it was there when the camera was first put in the tree several years ago.
When looking at an eagles' nest from the ground, some observers might think that the nest is hollow inside, but in fact the nest is solid and filled with sticks, food remains, and loamlike earth. The nest grows each year as the eagles add more sticks, in addition to adding sod, dead grasses, pine sprigs, moss, cattails, and corn stalks. As for our nest, we can make an estimate as to how wide the top platform is by looking at the female lying in the nest. Since the length of an average bald eagle female is about 36 inches, we can guess that the cam nest platform is maybe around four feet wide, if you include the outlying sticks.
Eagles will often build their nests in a fork or crotch near the top of the tree, with a few branches hanging over the nest (this is unlike the ospreys, which almost always build a nest out in the open). As for the shape, the tree's supporting branches will determine the structure's form, and biologists have categorized the shape of eagles' nests into the following styles: inverted cone, disk, bowl or cylinder shaped.
Historic Eagles' Nests
A well-built eagles' nest in a healthy tree can survive a very long time -- long enough that it might outlive the original owners and be used by more than one generation of birds. When talking about long-lived eagles' nests, there are two historic structures that come to mind. The first is a bald eagles' nest that was seen by Meriwether Lewis (of Lewis-and-Clark fame) while on the first U.S. overland expedition to the Pacific Coast (1804-1806). The Hidatsas Indians had told Lewis and Clark of an eagles' nest on the Upper Missouri River in Montana -- crucial information that helped the explorers confirm their location in the uncharted country. Lewis wrote down a description of the nest:
"below this fall at a little distance a beautifull little Island well timbered is situated about the middle of the river. in this Island on a Cottonwood tree an Eagle has placed her nest; a more inaccessable spot I beleive she could not have found; for neither man nor beast dare pass those gulphs which seperate her little domain from the shores."
An eagle and nest were seen at the same tiny island in 1830, 1860 and again in 1872, suggesting that the original nest had possibly survived for numerous decades. You can see the little island here.
Another famous bald eagle home was the massive, record-setting nest in Vermilion, Ohio, near Lake Erie -- a nest that was often referred to as simply "The Great Eyrie" (click thumbnail photo). Biologist Francis H. Herrick was the first person to study the amazing structure, which was built in 1890 and was twelve feet high, eight feet wide, and weighed almost two tons! In fact, the nest was so tall, it appeared to have multiple floors. The nest was in use until 1925 when it fell down during a storm, which scattered the newly laid eggs. Ten days later, the eagle parents started building a new eyrie only 431 feet away from where the old one had stood for so many years.
Until next time,
Lisa - webmaster
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