How Big Is a Bald Eagle Nest? Record Nests and Reuse

Typical bald eagle nest size

Bald eagles build the largest nests of any North American bird. A newly built nest is already a broad platform, big enough for two large adults and their chicks to stand on. Typical dimensions are:

The nest is built mainly of sticks and branches, some as thick as a human arm. The center is a shallow bowl lined with softer material such as grass, moss, pine needles, corn stalks, seaweed and the eagles’ own down feathers. Fresh green sprigs are often added during the season, possibly to freshen the lining or shade the chicks, although the exact reason is still debated.

How bald eagles build and add to their nests

Both members of a pair build the nest. They collect sticks from the ground or snap dead branches off trees, often carrying them in their feet, and weave them into the platform. A brand-new nest can take several weeks to about three months to complete.

What makes eagle nests so large is reuse. Bald eagles are strongly attached to their territory and usually keep the same partner for many years (see do bald eagles mate for life?). Each year, before egg laying, the pair repairs the nest and adds a new layer of sticks and lining. Over a decade or two these layers can turn a modest platform into a towering structure several meters deep.

Many pairs also maintain one or more alternate nests within their territory. They may switch nests from year to year, perhaps to escape parasites, after a disturbance or when a nest is damaged. As a result, a territory can contain several large nests even though only one is used in a given season.

Where bald eagles put their nests

Nest site choice matters more than the type of tree. Bald eagles typically pick one of the tallest and strongest trees near open water, often a large pine, spruce, cottonwood, oak or cypress, with a clear flight path and a view over the surrounding area. Most nests are within a few hundred meters of a lake, river or coast.

The nest usually sits in the top third of the tree, wedged in a fork of strong branches just below the crown, so the canopy gives some shelter from sun and wind. In Florida’s mangroves nests may be only about 6 m (20 ft) up. Where trees are scarce, eagles have nested on cliffs, rock pinnacles, transmission towers and, on some predator-free Alaskan islands, directly on the ground. In northwestern Mexico they have even been recorded nesting on top of tall cacti.

The record nest and other giants

The largest bald eagle nest ever measured was found near St. Petersburg, Florida, in 1963. It was about 2.9 m (9.5 ft) wide and 6.1 m (20 ft) deep, and its weight was estimated at more than 2 metric tons. It is often cited as the largest tree nest built by any bird.

Other famous nests were used for decades. One nest in the Midwest was occupied continuously for at least 34 years before it fell. Such giants are exceptional, though: most nests never reach this size because they are lost long before.

Golden eagles, ospreys and other large raptors also build bulky stick nests, and golden eagle cliff nests can grow very large over many years of use. But no other North American bird regularly matches the sheer bulk of an old bald eagle nest.

Why giant nests eventually collapse

Size has a price. A nest that keeps getting heavier eventually becomes too much for its supporting branches. Many nests are destroyed by storms, hurricanes or ice, and others fall when the branches below them rot or snap under the weight. In some cases the whole tree dies or topples, especially if the nest was built in a dead snag.

When a nest falls, the pair usually rebuilds nearby, often in the same tree or within the same territory, sometimes within weeks if it happens before the breeding season. If it happens while eggs or chicks are in the nest, that year’s breeding attempt usually fails, but the adults normally try again the following year.

Eagle nests and people

Because bald eagles are sensitive to disturbance during nesting, US federal guidelines recommend keeping construction, logging and loud activities well away from active nests, typically at least about 200 m (660 ft), and further in open areas. Nests themselves are protected by law even when the eagles are absent.

At the same time, many bald eagle nests now sit in plain view of the public. Livestreamed nest cameras in Iowa, Florida, West Virginia and elsewhere let millions of people watch pairs repair their nests, lay eggs and raise chicks each season. The chicks’ diet, delivered to the nest by both parents, is covered in what do bald eagles eat?.