The bald eagle builds the largest tree nests ever recorded for any animal species.
Bald eagle nests are enormous because breeding pairs reuse them and add fresh branches, moss, grass, and other material year after year. The record nest, discovered in Florida in 1963, measured about 2.9 meters across and 6.1 meters deep. Its great weight eventually threatens the supporting tree, and some giant nests collapse under their own mass or during storms.
Bald eagles usually choose tall, mature trees near water, where fish and other prey are available. Nest sites are often in conifers or hardwoods, but the species can also nest in mangroves, on cliffs, or on the ground where suitable trees are absent. Both members of a pair help build and maintain the nest.
The largest tree nest is not the same as the largest bird nest of every kind. Some birds, including malleefowl, construct huge ground-level incubation mounds rather than elevated nests. The bald eagle's record therefore refers specifically to a nest built in a tree, not to every nesting structure made by birds.