The oxpeckers’ special adaptations

Ndebele : Ihlalankomo, Shona : Tsande.

THE oxpeckers are two species of birds which make up the family Buphagidae.

These two species get their English names from the colour distinction of their bill and their habit of perching on large mammals (both wild and domesticated) such as cattle or rhinocerous pecking on ticks and other ectoparasites, thus the yellow-billed oxpecker — Buphagus africanus and the red-billed oxpecker — Buphagus erythrorhynchus. They are “tickbirds” endemic to the savanna of sub-Saharan Africa .

Their distribution is restricted by the presence of their preferred prey, specific species of ticks and the animal hosts of these ticks. Smaller antelopes such as lechwe, duikers and reedbuck are avoided, the smallest regularly targetted species is the impala probably because of the heavy tick load and social nature of that species.

Identification

The oxperckers are small to medium sized, solidly built birds. Their plumage is olive brown and paler below and on rump but the yellow-billed oxpecker has a paler yellowish buff on rump and rest of underparts than the red-billed oxpecker.

Their bill is stout and deep, yellow or red, medium length, laterally flattened and slightly hooked at tip. The legs are short and stout, feet are strong and toes are longish. The claws are sharply curved and needle-pointed.

The wings are long and pointed while the tail is moderately long and stiff. The claws and tail are used as support when perched on a vertical surface of large mammals and when climbing over the large grazing animals.

Feeding

They feed on ectoparasites particularly ticks and blood-sucking flies, the flesh, loose skin, wound tissue and blood of some wounds of host mammals. The birds do not simply divert their attention to the beasts' tissue when the parasites vanish, but they tend to disappear from the locality.

The yellow-billed oxpecker plucks its prey with its bill while the red-billed oxpecker uses a scissor-like bill action with the flattened bill laid sideways on the hide removing its prey. Because of its needle-sharp claws, the oxpecker can scamper rapidly in any direction — up and down a leg, under the belly and all over the  host’s face pecking on parasites.

The oxpecker/mammal interactions were originally thought to be an example of mutualism but recent evidence suggests that oxpeckers may be parasites instead. They eat ticks which would have already fed on the mammal host, and they have been observed to open new wounds and enhance existing ones in order to drink the blood of the animal. Some oxpecker hosts are intolerant of their presence such as the elephant and some antelope which will actively dislodge them when they land on them. In some cases the host shows an astonishing indifference, even when birds are nibbling at its sores.

Other hosts tolerate the oxpeckers while they search for ticks on their faces and it has been described as appearing to be an uncomfortable and invasive process. In some cases the oxpecker lives in a mutually symbiotic relationship with the rhinocerous, where both benefit from the relationship in that the oxpecker cleans off bugs and ticks from the rhino and at the same time gets food. This may be due to the fact that the rhinocerous skin is too tough to be damaged by the pecking of the oxpecker and it gets cleaned.

Distribution

The yellow-billed oxpecker is generally uncommon in Zimbabwe, only found in Hwange and Chizarira National Parks and west Matetsi in North western Zimbabwe, Gonarezhou National Park. It was               re-introduced into Matobo National Park. Its numbers are declining over the entire southern African range because of game eradication and reduction of ticks by cattle dipping.

On the other hand the red-billed oxpecker is a common resident in and around larger game reserves and it is rare to absent elsewhere. They are both found in the savanna and bushveld where they spend most of their time on large game mammals. They roost communally on large game mammals such as buffaloes at night, also in trees or reedbeds with a few on buildings.