White-bellied sea eagle
| White-bellied sea eagle | ||||||||||||
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White-bellied sea eagle ( Haliaeetus leucogaster ) |
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| Haliaeetus leucogaster | ||||||||||||
| ( JF Gmelin , 1788) |
The white-bellied sea eagle ( Haliaeetus leucogaster ) is a bird of prey from the family of hawks (Accipitridae) that is widespread in the Indomalayan and Australasian regions . With a body length of up to 85 centimeters, it is almost the size of the white-tailed eagle ( Haliaeetus albicilla ), but is overall slimmer and on average significantly lighter than this. Despite the wide distribution area, no subspecies are distinguished. The Solomon Sea Eagle ( Haliaeetus sanfordi ) is a sister species of the white-bellied sea eagle.
Appearance
The white-bellied sea eagle is unmistakable in its adult dress. The head, neck, front back and the entire underside of the bird are pure white. The plumage on the lower legs (trousers) and the upper cover feathers at the base of the tail are also colored. The upper side of the sitting bird is slate gray except for the areas described, all wing feathers are black. The beak of the adult white-bellied sea eagle is black at the tip of its beak and becomes lighter towards the base of its beak. The foot is not feathered and colored pale gray, the claws are black. In flight, a fully colored white-bellied sea eagle appears white except for the black wing feathers, which contrast sharply with the rest of the white of the wings. The wedge-shaped tail is also white except for two black lateral markings in the upper third of the tail.
Both juvenile and subadult plumage differ significantly from adult plumage. The pure white plumage parts of the adult bird are pale reddish brown in juvenile and subadult individuals and show distinct dark longitudinal stripes that change more and more into white from year to year. From the age of three, the white color of the tail becomes predominant, and the head and neck area is predominantly creamy white from this year of life. The upper side of the young birds is dark brown and from the age of three takes on the slate-gray color of the adult white-bellied sea eagle. In flight, young birds appear cream-colored without strong color contrasts. The 20 to 26 cm long tail (thrust) ends in a dark subterminal band. White-bellied sea eagles show adult plumage at the earliest when they are five years old.
The sexes do not differ in their plumage, but they do differ in size and weight. The females become about 20 percent larger and heavier than the males. Very large females reach a wingspan of almost 220 centimeters with a weight of approximately four kilograms.
voice
The calls of the white-bellied sea eagle can be heard especially in the mating season in the early morning and at dusk, occasionally also on bright nights. They are somewhat reminiscent of goose calls or nasal duck calls. White-bellied sea eagles often sing in a duet with their heads raised. The alarm call is a rough, rather jarring croak.
distribution and habitat
Light green : migration areas and occasional breeding areas.
Light blue circle: distribution area of the Solomon Sea Eagle Haliaeetus sanfordi
The white-bellied sea eagle is widespread in the coastal areas of the Indomalayic and Australasian regions, where it occurs on most of the islands in this area, except on the mainland. In places it is not uncommon in its area of distribution. Recently, population declines have been reported from Thailand and other areas of Southeast Asia.
It mainly inhabits coastal areas and the hinterland near the coast. The greatest densities are observed in mangrove forests at tidal estuaries. Occasionally it also inhabits habitats along large streams as well as the banks of lakes. Its main distribution is vertically mainly at sea level, but local occurrences up to 1500 m have been reported , on Sulawesi even from an altitude of 1700 meters. Rough population estimates range between 10,000 and 100,000 breeding pairs. Its entire population is currently not considered endangered. In the long term, however, as local inventory decreases suggest, the usual causes of danger, such as disturbances at the breeding site, direct persecution, habitat destruction and pesticide input can also become dangerous for this species.
Food and subsistence
The food range of the white-bellied sea eagle is very broad, it consists mainly, but by no means exclusively, of vertebrates living in and around water, such as fish, reptiles, birds and mammals. He also does not spurn carrion of all kinds, fish waste and waste in landfills. Sea snakes and small turtles predominate among the reptiles . Waders , shearwaters , terns and young herons , ducks, geese and cormorants make up the main prey among the birds. On mammals, it mainly preyed on various marsupial mammals and rodents, with the occasional gray-headed fruit bats also falling victim to it.
The hunting methods of the white-bellied sea eagle are varied and include both high seat hunting and slow flight hunting at different heights along the coastline or circles above the feeding grounds. Often times a couple hunt together. The prey is usually taken with one foot. Small prey animals are consumed in flight, larger ones carried to a preferred hide. The white-bellied sea eagle also hunts prey from other birds of prey and seabirds, occasionally brushing dormant bats off their roosts in flight or flies into a flock of water birds to separate a suitable victim.
Behavior and brood
White-bellied sea eagles have a lifelong partnership. The nest location is also used as a district center outside of the breeding season. During the courtship season, white-bellied sea eagles perform sightseeing flights accompanied by loud calls with impressive flight maneuvers, including mutual clawing and spinning. Concentrations of white-bellied sea eagles can be observed relatively often in favorable feeding places, young birds seem to roam in loose bachelor groups.
In accordance with the large distribution areas, breeding white-bellied sea eagles can be found regionally throughout the year. The nest is a voluminous structure made of branches and twigs that can be up to one and a half meters in diameter and three meters in height. It will be built by both partners and will be used for several years. The nest locations are very different: nests can be built in very tall trees, on platforms in the sea, on cliffs and rocks, but also in low bushes and even on the ground. The clutch usually consists of two, rarely one or three eggs. The young hatch after a incubation period of 35 to 42 days, the nestling period is around 70 days. It was fratricide observed whether it is obligatory Cainism is, is not known. Even after they have fledged, the young birds remain with their parents for up to six months until they are driven away.
hikes
Adult white-bellied sea eagles are annual birds, but make very long foraging flights. When food is scarce, for example as a result of drought, inland populations in particular lead a nomadic life. Young birds occasionally migrate over great distances. A young bird from South Australia was found 3,000 kilometers away on Fraser Island .
literature
- James Ferguson-Lees , David A. Christie: Raptors of the World. Houghton Mifflin Company, Boston, New York 2001, ISBN 0-618-12762-3 , pp. 108, 390-393.
Web links
- Birdlife international factsheet
- Haliaeetus leucogaster in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2004. Retrieved on January 25 of 2009.
- Videos, photos and sound recordings for Haliaeetus leucogaster in the Internet Bird Collection