Feeding preferences of the red-billed oxpecker, Buphagus erythrorhynchus: A parasitic mutualist?

The oxpecker-ungulate association of sub-Saharan Africa is an example of a complicated interspecific association subject to variation in outcome. Oxpeckers (Buphagus spp.) are unusual birds because they not only glean ticks from an array of African ungulates, but they are one of the few avian species known to wound-feed from their living hosts. The conditions under which oxpeckers wound-feed and the mechanisms generating variation in this association are unclear. We took a unique approach to studying the relationship by conducting a series of feeding preference experiments on twelve captive red-billed oxpeckers (B. erythrorhynchus). We assessed how oxpecker feeding behaviour is influenced by changes in tick abundance and tick type. In cafeteria-style experiments, oxpeckers fed equally on ticks and liquid bovine blood. In experiments using donkeys as the host animal, oxpeckers spent more time wound-feeding when a less-preferred tick type was available and when tick abundance was low compared to when a preferred tick type was available and when tick abundance was high. However, oxpeckers still wound-fed even when offered a large number of the ticks they prefer. Additional experiments incorporating tick species of different stages and multiple ungulate species are necessary to fully reveal the dynamics of this association.