About Bald Eagle Nests
Contributed by Laura Erickson

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Of all birds in the world, Bald Eagles hold the record for the biggest nest ever built. One nest in Florida was 6.1 meters deep, 2.9 meters wide, and weighed 2,722 kg (almost 3 tons). Could a Bald Eagle nest this size fit in your classroom?


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How can a pair of Bald Eagles possibly build that huge nest and still have time to lay eggs, incubate them, and raise the babies in a single breeding season?

The answer is, they don't! Throughout the season, and sometimes even during fall and winter, eagles keep adding sticks to the nest, and they reuse nests, continuing to build on to them, for many years. That huge record-breaking nest in Florida was the largest nest ever found, and it was very old. The average eagle nest is only 1.5-1.8 meters in diameter and 0.7-1.2 meters tall, and the first year a nest is built, it may be much smaller than that.

In most regions, a pair of eagles starts working on their nest from 1 to 3 months before the female lays the first egg. However, in the northern regions they can't delay this long. For example, according to Birds of North America, "In Saskatchewan, adults build or repair nests in September prior to migration and build or repair nests in April upon return from wintering grounds."

First Things First
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 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.

Building for the Future
Pairs usually start a new nest in a living tree, though there are often dead trees ("snags") nearby where they have a view all around when they're resting near the nest. The healthier the tree, the better. Eagles use and keep adding sticks to their nests for years and years. One well-studied Ohio nest was used for 34 years, until the tree finally blew down. Sometimes a tree with an eagle nest dies after many years. If the tree remains standing, the eagles often remain there as long as their nest is secure. But the healthier the tree is to start with, the longer it will last.

Going to the Lumber Store
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.

Interior Decorating
Eagles, along with several other hawks, add sprigs of greenery to their nests throughout the spring and summer. No one knows why they do this, but scientists have some ideas.

Before reading on, name as many reasons as you can think of why eagles might put greenery in their nests.

Answer: Some scientists think the greenery :

  • may serve as an insect repellent
  • may be a clear signal to other eagles that this nest is well-tended so they better keep away
  • may provide a bit of camouflage
  • may help keep inside of nest clean