- Gypohierax angolensis
Photographed: Mandina Bolong, Mandina lodges, Makasutu, The Gambia.
Identification
The adults have broad wings with white translucent primaries tipped black & obvious black secondaries. Immatures progress through a series of misleading plumages to adulthood including a phase where the primaries are black but the underwing coverts white.
The adult is mostly white, with 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 orange to red, the colour affected by emotional state and by the amount of palmnut oil consumed. 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.
This is an unmistakable bird as an adult. Its plumage is all white except for black areas in its wings. It has a red patch around the eye. The immature, which takes 5 years to mature, is brown with a yellow eye patch. In flight this species resembles an eagle more than a typical vulture, and it can sustain flapping flight, so it does not depend on thermals.
Distribution
Sub-Saharan Africa. Range closely coincides with that of the Oil Palm Elais guineensis. Breeds in Gambia and Senegal and from Sierra Leone east to Central Africa and south to northern Namibia, Northern Botswana and eastern South Africa. Locally distributed in East Africa found in southern Sudan, Uganda and western and southern Kenya but absent from most of Tanzania. Strictly resident. Common in West Africa but local and generally uncommon in the east and south although common on Pemba Island.
Taxonomy
The Palm-nut Vulture (Gypohierax angolensis) is a very large bird of prey in the family Accipitridae which also includes many other diurnal raptors such as kites, buzzards and harriers. It is the only member of the genus Gypohierax.
This bird is an Old World vulture, and is not related to the New World vultures which are in a separate family, Cathartidae.
Habitat
Found in tropical rainforest and heavily-wooded savanna areas and palm plantations. It breeds in forest and savannah across sub-Saharan Africa, usually near water, its range coinciding with that of the Oil Palm. It is quite approachable, like many African vultures, and can be seen near habitation, even on large hotel lawns in the tourist areas of countries like The Gambia.
Behaviour
It feeds largely on fruit of Oil Palm. Also found in mangrove swamps and harbours where feeds on fish.
This vulture gets its name from its favourite food, which, uniquely for a bird of prey, is not meat, but the nut of the Oil Palm. It will also take dead fish. One of the very few raptors to eat vegetable matter regularly, the Palm Nut Vulture eats the husk of oil palm nuts and raphia fruit husks as well as wild dates, upas and some other fruit. It also eats crabs, molluscs, etc, picked up on the sea shore, and stranded and occasionally live fish which are snatched from the water surface. Giant snails and locusts also feature occasionally. The diet of the adult will be up to about 60% fruits - that of the juveniles could top 90% fruits.
There are a number of calls. A growling 'pruk-kurrrr'; a contented, duck-like quacking at roost; and 'kwuk-kwuk-kwuk' when copulating. There is also a high-pitched 'tcheeeu'. In threat display it utters a grating 'karrrr'.
A breeding 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.
