White-bellied Sea-eagle (Haliaeetus leucogaster) and also known as the White-bellied Fish-eagle or White-breasted Sea Eagle, is a large bird of prey in the family Accipitridae which also includes many other diurnal raptors such as kites, buzzards and harriers.

It is resident from India through southeast Asia to Australia on coasts and major waterways. This large eagle is very distinctive. The adult has white head, breast underwing coverts and tail. The upperparts are grey and the black underwing flight feathers contrast with the white coverts. The tail is short and wedge-shaped as in all Haliaeetus species.[1]

Its closest relative is the little-known Sanford's Sea-eagle of the Solomon Islands. These form a species pair, and as usual in sea eagle species pairs, as opposed to the dark-headed Sanford's, the White-bellied Sea-eagle has a white head. Talons, bill, and eyes are dark as in all Gondwanan sea eagles. This species pair has at every age at least some dark colouration in its tail, though this may not always be clearly visible in this species. Although they differ much in appearance and ecology, their ancestors diverged less than one million years ago (Wink et al., 1996[2]).

The White-bellied Sea-eagle is the second largest bird of prey found in Australia. The largest is the Wedge-tailed Eagle, Aquila audax, which stands up to 1m. The Wedge-tailed Eagle is mostly brown, with a wedge-shaped tail.

It is white on the head, rump and underparts and dark grey on the back and wings. In flight the black flight feathers on the wings are easily seen when the bird is viewed from below. The large, hooked bill is grey with a darker tip, and the eye is dark brown. The legs and feet are cream-white, with long black talons (claws). The sexes are similar. Males (around 75cm in height) are slightly smaller than females (up to 85cm). The wingspan is about 2 m.[1]

Young Sea-eagles are brown when juveniles then gradually come to resemble adults, acquiring the complete adult plumage by their fourth year.