Palm nut vultures at Mahale

By Gabriel L Mushi - Guide, Greystoke Mahale

Vultures are birds of prey that typically depend on carrion for food. In Mahale there is only one species of vulture, the palm nut-vulture. The head, neck, back, rump, upper tail converts, and undersides of the adult birds are white, while the scapulars, secondaries, and greater upper wing converts are black.

The palm nut vulture is the most common large bird that you are likely to see when at Mahale. Their presence and abundance is linked to the oil palms, the fruits of which are their main food. This bird feeds on the brown-orange outer flesh of the oil palm fruits, as well as on the fruits of the wild date palm. Oil palm trees cover parts of the lowland areas of the Mahale rain forest. This tree is not native to Mahale, it was introduced by the Tongwe people who lived in this area before it was established as a national park. Palm nut vulture also scavenges dead fish from Lake Tanganyika, hence removing carrion. Since carrion can harbor diseases, the presence of palm nut vultures in Mahale is one good indicator of a healthy environment.

Unlike other vultures, the palm nut vulture often catches live prey---both on land and from the water. On several occasions I have seen them grabbing fish with their feet from the lake surface and then carrying the fish to a tree or to the lake shore to feed on it. Palm nut vultures also practice ‘kleptoparasitism’, that is, the behavior of stealing food from other species. They are known to steal food from white-napped ravens. Twice I have witnessed a palm nut vulture that was carrying food being chased by a white-napped raven. Presumably the vulture had taken the food from the raven.

Most of the time palm nut vultures are silent but they do call from their nest sites in the forest. They give a surprisingly loud, distinctive barking call. They lay one egg. Both sexes incubate the egg. Nestlings are covered with brown down. The presumed primary predators of the eggs and nestlings are vervet monkeys and yellow baboons.

Picture - Tom Butynski