Jen Guyton / Southern yellow-billed hornbills (Tockus leucomelas) guarding their nest hole in a tree, Kruger National Park, South Africa.

Loic Poidevin / Southern yellow billed hornbill (Tockus leucomelas) male in tree, Kenya

Ann & Steve Toon / Southern yellowbilled hornbills (Tockus leucomelas) courtship display. Kruger National Park, South Africa. September.

Richard Du Toit / Eastern Yellow-billed Hornbill (Tockus flavirostris) pair, Kruger National Park, South Africa

Yva Momatiuk & John Eastcott / Southern Yellow-billed Hornbill (Tockus leucomelas), Kruger National Park, South Africa

Wim van den Heever / Southern Yellow-Billed Hornbill (Tockus leucomelas) yawning while sitting on the ground, Sabi Sand Game Reserve, South Africa

Neil Aldridge / Southern yellow-billed hornbill (Tockus leucomelas) perched on a broken branch, Kruger National Park, South Africa.

Neil Aldridge / Portrait of a Southern yellow-billed hornbill (Tockus leucomelas) in early morning. Kruger National Park, South Africa.

Neil Aldridge / Portrait of a Southern yellow-billed hornbill (Tockus leucomelas) in woodland, Kruger National Park, South Africa.

Neil Aldridge / Southern yellow-billed hornbill (Tockus leucomelas) searching for food in leaf litter, Kruger National Park, South Africa.

Neil Aldridge / Southern yellow-billed hornbill (Tockus leucomelas) displays while calling in winter, Kruger National Park, South Africa.

Richard Du Toit / Yellow-billed hornbill (Tockus flavirostrus) in flight, Kruger National Park, South Africa.