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 to differences in host niche breadth. The redbilled oxpecker associates with at least 15 host species, ranging in size from impala to elephants (Stutterheim, 1976). Yellow-billed oxpeckers, on the other hand, select megafaunal hosts that have heavier tick loads and larger surface areas, specializing on buffalo (Syncerus caffer), eland (Tragelaphus oryx), giraffe (Giraffa camelopardalis) and rhinoceros (Diceros bicornis and Ceratotherium simum) (Attwell, 1966; Grobler & Charsley, 1978; Hustler, 1987).
