Palm-nut Vulture, Gypohierax angolensis (Gmelin 1788)

Physical appearance. The Palm-nut vulture is one of the smaller Old World vultures. The head is feathered and the plumage is mostly white, with black primaries on the wings and a red face and eye patch. The head, body and tail is 60 cm (24 in) long and the wingspan is about 150 cm (59 in). The average weight is 1.2-1.5 kg (2.6-4 lbs) (Fig. 2.3 a,b,c). The adult Palm-nut vulture is similar to the African Fish Eagle and the Egyptian vulture, but lacks the chestnut body feathers of the eagle and white tail of the Egyptian vulture. Juveniles are predominately brown with partially black wings and a yellow eye patch (Fig. 2.3 a,b,c).

Fig. 2.3. Palm-nut Vulture

Classification. The Palm-nut vulture, also called the Vulturine Fish Eagle, is the only member of the Genus Gypohierax Ruppell, 1836. As cited earlier, molecular studies have identified two clades of old world vultures; one comprising the hooded vulture Necrosyrtes and Gyps, with a sister group of Aegypius/ Torgos/Trigonoceps; and a second clade of the Bearded vulture (Gypaetus barbatus) and the Egyptian Vulture (Neophron percnopterus). The Palm-nut vulture of Africa is usually classified near the second clade (Wink and Sauer-Gurth 2004).

Foraging. Adults are largely sedentary, but juveniles are more mobile, and may wander beyond their breeding range into the northern Sahel Savanna and to the extreme south of Southern Africa, foraging on both plants and animals (Ferguson-Lees and Christie 2001). The prefered habitat is dense forest and treed savanna, usually near water, with and without oil and raffia palms, and also with and without human proximity.

The Palm-nut vulture eats fruit of the oil palm (Elaeis guineensis Jacq.), raffia palm (Genus Raphia P. Beauv.), and fruits and grains of other plants, which may comprise as much as 65% of its diet (del Hoyo et al. 1994; Ferguson-Lees and Christie 2001). However, other food sources exist; Thomson and Moreau (1957) describe it eating living fish in the Gambia. In East Africa, it occurs in the absence of oil-palms, subsisting partly on Raffia fruit. These authors argue that based on this evidence, and also on the 'survival of Gypohierax in zoos, it is concluded that the vitamin-rich oil-palm fruit is not essential to the bird; but one that had been in captivity for 11 years, when presented with the fruit, preferred that to its usual meat' (Thomson and Moreau 1957: 608). It also eats living small mammals, birds, reptiles, fish, invertebrates and amphibians, and scavenges on carcasses (Ferguson-Lees and Christie 2001; del Hoyo et al. 1994).

Breeding. The Palm-nut vulture nests in tall trees, using large stick nests. The breeding season is usually from October to May in West and Central Africa, June to January in East Africa, August to January in southern Africa and May to December in Angola (Ferguson-Lees and Christie 2001). It lays one white and chocolate-brown egg, which is incubated for four to six weeks, and the chick fledges in 85 to 90 days (Fig. 2.3d).

Population status. The distribution of the Palm-nut vulture is shown in Fig. 2.3e. It is a tropical African species, found from west and central Africa, where it is common, south to north east South Africa where it is rarer. In the northern and central latitudes of its range it is common to abundant, but it is rarer in the south and east. Due to its wide range and stable population, the Palm-nut vulture is not classified as vulnerable like other vultures (BirdLife International 2013). It is not known to be affected by pesticides or poisons (Del Hoyo et al. 1994). It is not persecuted by humans for food or medicine, but there are issues related to habitat loss in West Africa. Its range is related to the distribution of the oil palm, which has expanded in West Africa, Angola and Zululand for commercial reasons even if harvesting disturbs potential nesting sites (Ferguson-Lees and Christie 2001).