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Aug 27 2011

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Palm-nut Vulture (Gypohierax angolensis)

Palm-nut Vulture

[order] ACCIPITRIFORMES | [family] Accipitridae | [latin] Gypohierax angolensis | [authority] Gmelin, 1788 | [UK] Palm-nut Vulture | [FR] Palmiste africain | [DE] Palmgeier | [ES] Buitre plamero | [NL] Palmgier

Subspecies

Monotypic species

Genus

Members of the genus Gypohierax are small vulturine eagles, having long and broad wings, and a short, rounded tail. The bill is large, aquiline, and somewhat compressed. The lower legs are unfeathered and scaled, terminating in smallish, but curved and acute talons. The area around the eyes, and a streak running aft from the base of the bill are unfeathered. The adult is white with black wings and tail band, the young varying shades of brown.
The genus contains only one species, which is native to Africa.

Physical charateristics

The adult is mostly white, with for black scapulars, secondaries and wing coverts. The primaries are white with black tips, and there is some black mottling on the outer web. The tail is black with a white terminal band. The head is slightly crested. The iris is yellow, the cere grey, the bare skin of the face and feet are somewhere between flesh colour and yellowinsh orange. Males are only slightly smaller than females. The immature plumage is brown, darkest on the mantleand palest on wing coverts. The rump area is pale yellowish brown. Primary flight feathers are black. The transition to adult plumage is, like that of the Egyptian Vulture, a lengthy affair, taking at least three to four years. In the field adults can only be confused with the African Fish Eagle and Egyptian Vulture. From the African Fish Eagle they can be distinguished by smaller size, rounded wings with white primaries, and black, white-tipped tail: from the Egyptian Vulture by the white primaries and square tail. Immatures could be confused with immature Egyptian Vulture, but for the square tail; with immature Hooded Vulture, but for their heavier and more powerful bill and feathered head and neck; and with immature Gymnogenes, from which they can be distinguished by rounded wings, short tail, and entirely different general appearance and style of flight, being stouter in body, and flying with quick wing beats followed by short glides.


wingspan min.: 140 cm wingspan max.: 160 cm
size min.: 55 cm size max.: 65 cm
incubation min.: 42 days incubation max.: 46 days
fledging min.: 90 days fledging max.: 110 days
broods: 1   eggs min.: 1  
      eggs max.: 1  

Range

Africa : West, Central, Southcentral, Southeast. The Palm Nut Vulture or Vulturine Fish Eagle can only be found in the forested and savannah regions of Africa south of a line from Kenya across to Gambia and south to the Cape Province. Its range is almost exactly the same as that of the oil palm Elaeis guineensis.

Habitat

This is a curious bird which lives almost entirely in country where the oil palm occurs; forest, mangrove, or the wetter savannahs of West and Central Africa. It is most common in mangrove swamps. It has been seen at up to 6,000 feet in Kenya, but is most common at 2,000 feet or less.
It is a tame and confiding bird, showing curiosity towards man in many areas. In mangrove swamps it can often be seen perched in a high tree, or scavenging on the shore. It feeds from sunrise and also late evening, competing with some other birds, notably Harrier Hawks and hornbills, for the husk of oil palm nuts. It will visit the same palm day after day as long as the fruit lasts. Its distribution is not absolutely confined to that of Elaeis, but it must have either oil or Raphia palms, on the fruit of which it also feeds. It is a sedentary species, often spending all its life within quite a short range of the breeding site, roosting close to or in the nest tree. It is usually found beside large rivers, streams or lakes, but does occur far from considerable stretches of water in savannah country, and may breed miles from water, or even from a supply of oil palm nuts.

Reproduction

A pair are attached to their nest site, and may be found closely associated with it all the year round. At the onset of the breeding season they perform a rolling and diving flight together, and roost nightly in their nest tree. Copulation takes place at or near the nest site just before egg-laying.
Nests are built in large trees, at a height of anything between 30 and 200 feet. They are made of sticks, adorned with oil palm racemes. They are large structures, about three feet across and one-and-a-half feet deep, often in a large main fork of whatever tree is selected. Building and repair, which is carried out by both sexes occupies four to six weeks. Only one egg is laid, white, heavily marked with dark brown and chocolate, with lilac and pale brown undermarkings. The duration of the incubation period is between six and seven weeks (about 44 days). The fledging period is long, frequently more than 90 days, giving a total breeding cycle time of about five months.

Feeding habits

One of the very few raptors to eat vegetable matter regularly, the Palm Nut Vulture, true to its name, eats the husk of oil palm nuts and raphia fruit husks. True to its other name of Vulturine Fish Eagle, it also eats crabs, molluscs, etc, picked up on the sea shore; also stranded and occasionally live fish which are snatched from the water surface. Giant snails and locusts also feature occasionally. Oil palm nuts are such a favoured food, that it will often reject meat in favour of oil palm husk.

Video Palm-nut Vulture

httpv://www.youtube.com/watch?v=H-YsjSMWz70

copyright: Dave Jackson


Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Palm-nut Vulture status Least Concern

Migration

Sedentary in most areas with plentiful palm fruit. Also resident in some East African coastal areas with few palms, feeding mainly on crabs, fish and carrion. A regular vagrant to drier parts of South Africa, as well as to northern savannas of West Africa, suggesting some dispersal of non-breeding adults and juveniles; also vagrant to drier sub-Saharan areas outside normal range.

Distribution map

Palm-nut Vulture distribution range map

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