Red-billed oxpeckers: vampires or tickbirds?

Abstract

Many recent studies have shown that classic examples of mutualism are either far more complicated than originally believed, or that they are not mutualisms at all. Red-billed oxpeckers (Buphagus erythrorhynchus) are just such an example of an “adaptive story.” These small birds feed almost exclusively on what they can glean from the skin of large African mammals. The relationship is obligate for the birds, and it is generally assumed that hosts benefit through a reduction in tick load. Although widely accepted in the literature, this theory has never been tested in the field. I excluded oxpeckers from cattle as part of a controlled field experiment in Zimbabwe to test this idea. Changes in adult tick loads were unaffected by excluding the birds. In addition, oxpeckers significantly prolonged the healing time of wounds and removed earwax. These results suggest that the oxpecker-mammal relationship is more complex than was previously thought.