Richard Du Toit / Red-billed Oxpecker (Buphagus erythrorhynchus) group on White Rhinoceros (Ceratotherium simum), Kruger National Park, South Africa

Richard Du Toit / Red-billed Oxpecker (Buphagus erythrorhynchus) group on White Rhinoceros (Ceratotherium simum), Kruger National Park, South Africa

Richard Du Toit / Impala (Aepyceros melampus) male with Red-billed Oxpecker (Buphagus erythrorhynchus) pair, Kruger National Park, South Africa

Pal Hermansen / Yellow-billed oxpecker (Buphagus africanus) on African buffalo (Syncerus caffer), Masai Mara, Kenya

Heini Wehrle / Red-billed Oxpecker (Buphagus erythrorhynchus) pair searching for parasites on Impala, Mpumalanga, South Africa

Sergey Gorshkov / Red-billed Oxpecker (Buphagus erythrorhynchus) trio on White Rhinoceros (Ceratotherium simum), Sabi-sands Game Reserve, South Africa

Yva Momatiuk & John Eastcott / Cape Buffalo (Syncerus caffer) bull with Red-billed Oxpecker (Buphagus erythrorhynchus) pair, Masai Mara National Reserve, Kenya

Richard Du Toit / Hippopotamus (Hippopotamus amphibius) male with Red-billed Oxpecker (Buphagus erythrorhynchus) pair on back, Chobe National Park, Botswana

Mitsuaki Iwago / Cape Buffalo (Syncerus caffer) eyeing Red-billed Oxpecker (Buphagus erythrorhynchus), Serengeti National Park, Tanzania

Mitsuaki Iwago / Black Rhinoceros (Diceros bicornis) with Red-billed Oxpecker (Buphagus erythrorhynchus), Serengeti National Park, Tanzania

Richard Du Toit / Red-billed Oxpecker (Buphagus erythrorhynchus) on Impala (Aepyceros melampus) male, Kruger National Park, South Africa

Shin Yoshino / Yellow-billed Oxpecker (Buphagus africanus) trio sitting on Cape Buffalo's (Syncerus caffer) head, Kenya