Dave Taylor's African Safari: Trophic Level III: Omnivores and Small Carnivores - Yellow-billed Oxpecker

Trophic Level III: Omnivores and Small Carnivores
Yellow-billed Oxpecker
Page 31

Buphagus africanus

Length: 22 cm (8.5")

Status: Common

Habitat: Yellow-billed oxpeckers are found in grasslands, wooded savannas, riverine forests and forest edges.

Food: Oxpeckers are the only species to feed on the ticks and flies that pester larger animals. They land on rhinos, buffalo, giraffes, wildebeest, zebras, antelopes and even warthogs where they poke about the animal’s hide, eating blood-engorged ticks. The ticks are a parasite and feed on the host’s blood.

In fact, it is the blood the birds want more than the ticks. They also eat a species of blood-sucking fly (Stomoxys). Oxpeckers are not above taking blood and tissue from the host animal either.

Surprisingly, many of the host mammals tolerate and even seek out the birds. Oxpeckers are very alert and will fly off if they spot danger, thus warning the antelope or rhino. This is an example of a symbiotic relationship.

Host animals often appear to signal their willingness to be groomed by the oxpeckers. Zebras will stand still and raise their head. Other species also seem to stop their normal feeding behavior to accommodate these birds. The communication between two species is not well studied but there does seem to be something unusual going on, at least between zebras and oxpeckers. Oxpeckers, when they wish to probe the dark, black skin around the zebra's anus, will hop down the animal's back. The zebra responds by lifting its tail so the bird can access that area. The only other time a zebra lifts its tail is to defecate.

The benefit to the host animal is that it has bothersome ticks and maggots removed. How bothersome are they? No study has been done on African wild animals but one study using African cattle did produce some interesting evidence. It was shown that a single tick can drink enough blood to decrease a calf's weight by half a kilogram (1 pound) a year. If this is true for African mammals (and it probably is), then the oxpeckers are doing them a real service

Oxpeckers seldom, if ever, are seen on elephants. They never feed on long haired mammals such as waterbuck.

Social System/Behavior: In the Serengeti-Mara ecosystem, there are two species of oxpecker that are likely to be seen. Both occupy similar niches and both feed on the same food. Yellow-billed oxpeckers and red-billed oxpeckers resemble each other in many of their behaviors. Their feeding is virtually identical.

Nesting habits are different. Within each flock of red-billed oxpeckers, only the dominant pair breeds. In flocks of yellow-billed oxpeckers, birds pair up to breed. Both species nest in tree cavities lined with a cup of grass, straw and mammal hair.

The red-billed may raise three broods a year. The yellow-billed raises only one.

Yellow-billed oxpeckers lay two or three eggs; red-billed lay three. They are cooperative nesters with one or more young from the previous year assisting in raising the next season's offspring. The brood of two or three nestlings will spend a month in the cavity where they are fed by all members of the group. After fledging, they spend another month being fed by their parents. They can often be seen begging for food on a zebra's back.

Oxpeckers spend much of their day on their mammal hosts. They even mate there.

Predators: As with other starlings, the main predators are hawks, falcons and small mammalian carnivores.

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