* In New Latin, Haliaeetus = sea-eagle, from Ancient Greek haliaetos = sea-eagle or osprey, derived from hali = at sea, and aetos = eagle; leucogaster from Greek leuco = white, and gaster = belly.

Other common names: White-breasted Sea-eagle, White-breasted Fish-eagle, White-breasted Fish Eagle.

Taxonomy: Haliaeetus leucogaster (Gmelin) 1788, Java.

Sub-species & Distribution: A monotypic species, found in coastal areas from India, China, Taiwan and the Philippines, south to mainland SE Asia, and east to New Guinea, Australia and Tasmania.

Size: 29 to 33" (75 to 85 cm). Sexes similar.

Description: A large raptor with long, broad wings that, when folded, extend beyond the tip of its short, wedge-shaped tail. Head, neck and entire underparts pure white. Upperparts pale grey, sometimes with very fine black shaft streaks on the neck and breast (Oates 1895), the uppertail coverts much darker. Wings grey, becoming browner with wear, the primaries black, whitish at base. The basal two-thirds of its wedge-shaped tail is black, the terminal third pure white, the underwing coverts and axillaries white (Robinson 1927), contrasting with black flight feathers.

Females: Like males but much larger, the adults being difficult to sex except when seen together.

Soft parts: Iris reddish-brown. Bill dull bluish-grey, paler along edges of mandibles, black at tip. Cere paler bluish-grey. Tarsus not feathered, legs and feet pale flesh to dirty white, claws black.

Immature plumages: The transition from juvenile to sub-adult and adult plumages is a slow and gradual process. After a series of annual moults, young birds acquire sub-adult plumage and start to resemble adult birds. Full adult plumage is attained only in the fourth or fifth year.

Juveniles: Head, neck, chin and throat brown, the feathers edged with reddish-buff, paler and broader on the crown and hind-neck. Upperparts dark brown, the feathers broadly edged with pale reddish-buff. Wings largely dark greyish-brown, the wing coverts edged with buffy-brown. Tail white or whitish basally, mottled white and brown distally, the tips being brownish-grey. Underparts pale brownish, the feathers washed with yellowish-buff, darker and more reddish-brown on the breast.

Seen from below, the trailing edges of the wing are uniformly serrated (Ferguson-Lees & Christie 2001). The lesser underwing coverts show as white, heavily marked with black and, less so, with rufous-buff, median underwing coverts more rufous-buff and greater underwing coverts white with black tips. Much of the primaries and secondaries appear uniformly black except for a white panel formed by the pale outer webs of the primaries.

Second-year: Similar to juvenile. Head whitish-buff, back and wings pale greyish-brown, wing-coverts more evenly dark, the tail mainly white with a much thinner sub-terminal band most obvious at corners. From below, the tail appears white, the undertail coverts, belly, flanks and lower breast pale rufous-buff, breast and thighs darker, the trailing edges of the wing mainly even, but some old juvenile secondaries remain (Ferguson-Lees & Christie 2001). The underwing coverts seem almost white though still mottled with black and rufous-buff, and the white panel on the underwing remains evident.

Third-year: Head and underbody creamy-white, the breast and thighs streaked with buff, the tall white with some blackish mottling at base, sometimes uneven and extensive. The underwing coverts pale buff and more white on bases of secondaries, the white panel on the underwing still evident (Ferguson-Lees & Christie 2001).

Sub-adult: Back and wing-coverts largely grey, base of tail almost all black, some buff still showing on thighs and breast and underwing coverts, and some white on underwing at the base of flight-feathers (Ferguson-Lees & Christie 2001).

Similar species: Seen from below, the White-bellied Fish Eagle, very much larger and much less active than a Brahminy Kite Haliastur indus, can easily be recognised by its wedge-shaped white-tipped tail, its black primaries and secondaries contrasting with white underwing coverts and white underparts. Adult Brahminy Kites have dark chestnut underwing coverts, rounded chestnut tail and chestnut wings, only the wing tips being black. Immature Brahminy Kites can be separated by their smaller size, dark brown to chestnut lower belly, thighs and vent, and rounded tail.

Status, Habitat & Behaviour: A common resident, singly or in pairs, throughout Singapore (Wang & Hails 2007) - see Singapore Distribution Map. It occurs mainly along the coastline, and on nearly every rocky islet, keeping to the same territory year after year (Robinson 1927), also in open country around large lakes and along larger rivers some distance from their mouths though, according to Robinson (1927) rarely travelling far inland beyond the tidal reaches of rivers. It has been seen as far inland as Kuala Lumpur (Gibson-Hill 1949), and up to 900m, and 1700m on Sulawesi (Ferguson-Lees & Christie 2001).

It uses several hunting strategies. Sitting conspicuously out in the open, on its favourite perch, high on a tree overlooking water, a fishing stake or on rock faces on outlying islands, it will watch patiently for prey. It also quarters its feeding territory, by gliding along the shoreline or flying with steady powerful wing beats about 15 to 20 m above the water. Alternatively, it circles the area in soaring flight, using thermals to gain height, its wings raised into a V-shape, the outer primaries splayed out like fingers.

Once the quarry is sighted, with wings half-folded, it dives steeply down before flattening out into a low fast glide over the water and, with a backward flick of one talon, pluck a fish (see Wee & Chan 2007) or sea-snake (see Kwong 2010) from near the surface, its foot hardly making a splash, before rising with the victim dangling from its claws. Large prey items are taken back to the perch where it is thoroughly dismantled and eaten (Ali & Ripley 1968), the smaller ones usually eaten in flight, and carrion often eaten on ground (Ferguson-Lees & Christie 2001). Though they have been known to hover low over the water to take prey, rarely do they land in the water. When paired, both birds may hunt together, often to hunt other birds or to harass and steal food from them. They are, in turn, often mobbed by smaller birds (see Amar-Singh 2009).

During the evening, one or two can be seen slowly flying towards well-known roosts on top of tall trees in various parts of the island, often within the city limits. Some of these roosts have been in use for many years (Robinson & Chasen 1939).

Adults are generally sedentary and do not migrate. Mated pairs tend to stay near their nesting site and forage over wide areas. Immature birds and unpaired adults, however, may disperse some considerable distance (Ferguson-Lees & Christie 2001).

Food: It feeds mainly on fish, captured alive near the surface of the water or dead fish on the beach. Its extended menu, summed up by Jerdon (1862) as "anything living it can catch", includes sea snakes as they bask on the surface of the water (Bucknill & Chasen 1927), small turtles and tortoises, cuttlefish, crabs and birds taken in flight (see Teo 2007). On land, it takes rats, lizards, frogs, domestic fowl and birds. It will fight to take possession of a fish captured by another bird (Ridley 1898) and habitually pursues ospreys to rob it of its catch (Jerdon 1862). Crabs are dropped from a height on to rocks to break the shell (Tweedie 1960), and any carrion lying about is not despised (Baker 1928). It also takes fish from seine nets (Robinson 1927). In India, it was seen taking a salt-water crocodile Crocodylus porosus hatchling (Gopi & Pandav 2006).

It snatches fruit-bats from tree-roosts, harries waterbirds to separate out a suitable victim, forages on rubbish dumps, follows dolphins for disturbed prey, hunts co-operatively as a pair, and has been seen taking wallabies in Australia (Ferguson-Lees & Christie 2001).

Voice and Calls: Its very loud clanging cry of many notes, heard usually in the mornings and evenings when they are most noisy, is audible at a great distance (Baker 1928).

It is especially noisy during the breeding season. Just prior to copulation, the female gives a loud, nasal and metallic kãnk-kãnk-kãnk-kãnk, the male responding with a series of rapid ken-ken-ken-ken notes, uttered up to ten times, repeatedly for about three minutes, with breaks in between (Ali & Ripley 1968). It also has a loud barking, or rather yelping, cry (Bucknill & Chasen 1927).

Breeding: Many coastal nesting sites have been lost due to development and, currently, nesting occurs mainly in the central forested areas. In Singapore, mating and courtship has been recorded in May and December; nest-building from January to April, June and October; nestlings from January to May, and August; and juvenile birds in March, April and June (Wang & Hails 2007). Elsewhere along its extended range, it breeds between October to March in India, and between May to November in New Guinea and north Australia. The birds either build a new nest or refurbish one they had previously used.

The nest is usually placed on trees overlooking steep cliffs and rock faces by the sea or, where there are no trees, on the cliff and rock face itself (Hume 1890). They may nest 70m up on tall trees along the edges of forests and, in Singapore and Malaysia, on top of commmunication towers. On islands, it may be placed on low bushes, even on the ground (Ferguson-Lees & Christie 2001).

The nest, about 1.5m in diameter and placed between two branches of a tall tree, is a large platform of small branches, sticks and twigs, with a slight central depression (Hume 1890), sometimes with a lining of green leaves (Oates 1895), grass and seaweed (Ferguson-Lees & Christie 2001). Where the same nests are used year after year, with a few sticks added each year by way of repairs (Hume 1890), old nests tend to get very large. A nest in the Nicobars was more than 2.7m across and many nests up to 1.8m deep. The birds are wary and shy when nesting far from human habitation, but at nesting sites close to an urban setting, the birds take no notice at all of human beings (Baker 1928). Both partners share duties in nest-building, also during incubation and caring for the young and, jointly, vigorously defend their nesting territory (Tan 2009) against all intruders.

Since they mate for life, White-bellied Sea Eagles are often seen in pairs. Once paired up, they can be seen around their nesting site all the year round, regularly returning to the nest after each foraging trip and using it as a larder and a refuse-pit for fish and snake bones and other waste food. At night, they roost close to the nest, whether breeding or not (Hume 1890). Some nests, known to have lasted for at least thirty or forty years, have become conspicuous landmarks on the coast (Bucknill & Chasen 1927).

During courtship, both partners soar near and above over the nest area, singly or together, duetting in flight and from perches (Debus 2008). Aerial displays include mutual low- and high-circling, twisting and turning chases, dives and somersaults, and parallel-flights leading to talon-grappling and cart-wheeling (Ferguson-Lees & Christie 2001). However, it has been suggested by Debus (2008) that, as in similar cases of such behaviour in raptors, the talon-grappling and cart-wheeling flights may represent fighting between rivals, rather than courtship displays between mated pairs. In this context, there is a report of these eagles, when attacked by crows, attempting to defend themselves by turning onto their sides and striking with their claws, sometimes over-balancing themselves and turning completely over, executing a kind of lateral somersault (Ridley 1898). While such behaviour cannot be excluded as part of courtship rituals, it is clearly used as part of their defence strategy, immature birds often being seen practising the art (see Wee, Chan & Lee 2007) with others of the same species.

It usually lays two, sometimes three, pale greenish-white eggs, the average size of twenty-two eggs being 72.2 x 53.8 mm (Baker 1928). Incubation takes 40 to 42 days, the female bearing the greater share of it, the male relieving her for about an hour each time, allowing her to forage for food (Debus 2008). The nestlings are covered in down during the first four weeks, and, by the tenth week, are mostly feathered and feeding themselves on prey left in the nest. They fledge after 65 to 70 days according to Ferguson-Lees & Christie (2001), though Debus (2008) says it takes 81 to 84 days.

The fledglings, dependent on their parents for at least 2 months, stay close to the nest, and roost at night on nearby branches. Some of them stay within parental territory almost until the start of the next breeding season, about 6 months after fledging, without being expelled by their parents (Debus 2008).

Moult: Large Accipitrids do not undergo complete wing and tail moult annually. Since each of their large wing quills may take as long as 40 to 60 days to grow, conventional moult strategies (see Newton 2009) can leave large gaps among the flight feathers and seriously impair flight performance.

The White-bellied Sea Eagle, being sedentary, replaces its flight feathers in consecutive moult waves, a slow process called serial moult (see Edelstam 1984).

Immature sea-eagles completely replace their primaries within two to three years and, when in flight, the contrast between flight feathers of different moult groups can be detected. Primary moult in adults takes over three years to complete.