Despite generally being seen singly or in pairs (2) (4) (5), the white-bellied sea eagle is known to occasionally congregate in areas where there is abundant food available (4). While immature white-bellied sea eagles tend to disperse from the area in which they hatched, most adults of this species are sedentary, although they are capable of travelling long distances in search of food or in response to drought conditions (4).
This species feeds on a wide variety of aquatic species, including fish, sea snakes, water birds and marine turtles (4) (8) (10) (11) (16), but may also prey on land mammals (4) (8) (16), including domestic livestock (4).
Foraging flights generally occur over large expanses of open water, but may sometimes take place over open terrestrial habitats, including grasslands (4). The white-bellied sea eagle makes shallow glides over the surface of the water, performing spectacular swoops and dives to snatch its prey (2) (7) (10) (11), usually with one foot (4) and without entering the water (9) (11). This species also feeds on carrion (2) (8) (11), and is known to steal prey from other birds (2) (4) (9) (11). Interestingly, the white-bellied sea eagle has been recorded following dolphins, to catch flushed prey. If small, prey items are usually consumed in flight, but larger items are generally carried back to a feeding platform, or are occasionally eaten on the ground (4).
It is thought that the white-bellied sea eagle is capable of breeding at around 6 years of age, and may live for up to 30 years, although the mortality rates of young, newly independent birds is high (4). Following an acrobatic courtship display that includes somersaults and stoops (3), the white-bellied sea eagle forms a monogamous pair that mates for life and defends a breeding territory against other sea eagles (4). Should one of the pair die, it is soon replaced (4).
In southern Australia, the breeding season of the white-bellied sea eagle extends from June to January or February, while in northern Australia it tends to start one or two months earlier (4), lasting from May to October on Barrow Island off Australia’s northwest coast (8). The white-bellied sea eagle’s large nest, which can be two to three metres across and up to four metres deep (17), is built with sticks and lined with leaves, grass and seaweed (4) (8) (9) (10). The nest is often built in a tall tree near water (9) (11), although sometimes mangroves, cliffs, caves and rocky outcrops are used as nesting sites (4). The same nest may be used year after year (4) (8) (10).
White-bellied sea eagle eggs are white in colour and are laid in clutches consisting of between one and three eggs (4), with two being most common (4) (8) (10). The eggs are incubated for about six weeks, mostly by the female (4), although the male will sit on the eggs while the female feeds (8). White-bellied sea eagle chicks are fed by both adults, and do not leave the nest until 65 to 70 days after hatching. The adult birds continue to feed their young for up to three months after the fledglings have left the nest, but will then drive the young birds out of the breeding territory. In two-egg clutches, typically only one young is fledged, and if a clutch is unsuccessful, adult pairs will lay a second clutch (4).