The bald eagle is a powerful and opportunistic forager, feeding on a variety of prey including mammals, birds, reptiles, amphibians, crustaceans, carrion, and even garbage, although fish are preferred. Prey may be captured directly, scavenged, or stolen from other bald eagles or from other species. Birds, up to the size of geese, may be taken on the wing, while fish are usually taken from the water surface, or alternatively by wading into water, or by searching for dead or dying individuals (2) (3) (5). Cooperative hunting may also sometimes occur, one eagle flushing prey towards another (8). Bald eagles may gather in large groups at feeding sites, such as where salmon come to spawn, and often concentrate in large numbers of up to a thousand or more individuals at winter roosts (2) (3) (5).
The bald eagle is monogamous, and thought to pair for life, reinforcing the pair bond through spectacular, acrobatic flight displays that include the pair flying to a great height, locking the talons, and cartwheeling towards the ground, only breaking off at the last moment (2) (5). The breeding season of the bald eagle varies with location, ranging from April to August in Alaska and Canada, to November to March in southern USA (2) (3). Breeding pairs become highly territorial during this time (2). The nest is usually built in a large tree, or sometimes on the ground or a cliff. Both sexes help construct the nest, which is built with sticks and lined with grass, moss, seaweed or other vegetation. Material may be regularly added over many years, leading to one of the largest nests of all birds, the largest on record measuring a remarkable 2.9 metres across and over 6 metres deep (2) (3) (5). One to three white eggs are laid, and hatch after an incubation period of around 35 days. The young bald eagles fledge at around 75 to 80 days, but remain dependent on the adults for up to a further 6 weeks (2) (3). Young bald eagles do not start to breed until the fifth year, and are potentially long-lived, at up to 28 years in the wild and 36 years in captivity (2).