December

Nest Building/Repairing
In most regions, a pair of eagles starts working on their nest from 1 to 3 months before the female lays the first egg.

Nests are typically located in one of the taller trees in an area, just below the crown, about 3/4 the way up the tree, against the trunk or in a sturdy fork of the tree. Assorted interwoven sticks up to 1 inch or more in diameter make up the bulk of the nest. The nest is lined with soft grass, moss, or other fine materials. Nests can take months to complete, are added to each year, and in exceptional cases can end up weighing several tons.

Territory Defense and Nest Building: 1 - 3 months
Eagles are tricky to study because the male and female look so much alike, and because they are so wary of humans near their nest. Some pairs may approach nesting in a different way than others, but it's hard to be sure. Scientists have observed some mating behaviors on wintering grounds, but have also seen some males and females start courting in breeding areas. Females seem to be the ones who choose the territory and the nesting tree, because when a female loses her mate, she usually very quickly attracts a new male, even if she's already sitting on eggs fertilized by her first mate.
Both the male and female bring nesting materials; some eagle researchers believe it's the female who usually places the sticks in the nest. It takes from 1 - 3 months to build an eagle nest. Once it's built, a pair often uses it year after year, adding sticks and fresh plants and working on construction at the beginning of the nesting season. Also, many times the pair makes nest repairs or builds onto the nest for a while after the babies have left for the season.

Both the male and female defend their territory against possible predators, especially ravens and other raptors. In defending the territory against other Bald Eagles, usually males chase off other males, and females chase off other females.

In addition to defending the area from intruders, both males and females help to build the nest. If it's not their first year on the nest, they just add to the same nest used in previous years. The branches used can be up to 6 feet long and 2 inches thick. The biggest nest I've ever seen was in NY, and was about 12 feet deep and 7 feet across. Since they add to their nest each year, they can get very big and heavy. One nest in Florida, which finally caused the tree to fall down, was reported to be 22 feet deep and weighed over two tons!

When a young pair of Bald Eagles needs to build a brand new nest, their first job is to find a place for it. They probably prefer a territory close to water, where they can catch fish for their babies without wasting time flying back and forth a long distance, but in some areas they may nest several miles from fishing areas. In parts of Alaska and northern Canada, where trees are scarce and short, eagles often nest on the ground. In forested areas, they usually select one of the tallest trees in the area. If this is a "super-canopy" tree (one sticking up above nearby trees) the eagles can see all around, and also can fly into the nest without bonking their huge wings into branches. In Canada and the northern and western states, eagles almost always select a coniferous tree, usually a pine, spruce, or fir. In the eastern states, where large conifers may not be available in otherwise good habitat, eagles are more likely to nest in an oak, hickory, cottonwood, or other large leafy tree.

Caption Page: Building Supplies?
Where do eagles get the sticks for their nest? They pick up broken sticks from the ground, and sometimes break branches off trees. They naturally take as many sticks as they can find close to the nest, but may lug some branches as far as a mile, carrying them in their talons. They usually start building in the top quarter of the tree, below the crown, near the trunk, where branches are thick and strong enough to support the heavy nest. They interweave the sticks, and fill in spaces with grasses, mosses, cornstalks, Spanish moss, and other fibers. Looking at an eagle's nest, it's hard to understand why eggs don't get cracked or babies don't get poked by the sharp sticks. To soften the bottom, parents line it with their own feathers.

Caption Page: BIG Nest
The bald eagle is an opportunistic feeder which subsists mainly on fish, which it swoops down and snatches from the water with its talons. It builds the largest nest of any North American bird and the largest tree nests ever recorded for any animal species, up to 4 m (13 ft) deep, 2.5 m (8.2 ft) wide, and 1 metric ton (1.1 short tons) in weight.

Bald Eagles build some of the largest of all bird nests—typically 5 to 6 feet in diameter and 2 to 4 feet tall, and ranging in shape from cylindrical to conical to flat, depending on the supporting tree. Both sexes bring materials to the nest, but the female does most of the placement. They weave together sticks and fill in the cracks with softer material such as grass, moss, or cornstalks. The inside of the nest is lined first with lichen or other fine woody material, then with downy feathers and sometimes sprigs of greenery. Ground nests are built of whatever’s available, such as kelp and driftwood near coastal shorelines. Nests can take up to three months to build, and may be reused (and added to) year after year.

Facts and Photos

• Nesting Timeline
• Building Supplies
• How Eagles Build a Nest
• Whose Job Is It?
• BIG Nest