Oxpeckers are obligate mammal gleaners, feeding on ectoparasites and dead skin of large herbivores (Bezuidenhout & Stutterheim, 1980; Dean & MacDonald, 1981). There are two sympatric species in sub-Saharan Africa: the red-billed (Buphagus erythrorhynus) and yellow-billed oxpeckers (Buphagus africana). The red-billed species is smaller, with a scissor-like bill, while the yellow-billed species is larger, behaviourally dominant, and has a broad, flat beak (Attwell, 1966; Neweklowsky, 1974; Stutterheim, Bezuidenhout, & Elliott, 1988). These behavioural and morphological attributes are hypothesized to contribute