Staffan Widstrand / Wild Wonders of China / Great pied hornbill (Buceros bicornis) male bird photographed in flight in Hong Bung He, Dehong, Yunnan, China

Neil Aldridge / Southern ground hornbill (Bucorvus leadbeateri) juvenile with an adult bird close by on the Selinda Reserve in northern Botswana. Vulnerable.

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

David Tipling / Huli Wigmen from the Tari Valley in Southern Highlands of Papua New Guinea, wearing a bill from Blyth's Hornbill as decoration, August 2011

Daniel Heuclin / Traditional bush hunter with a calao / Hornbill head decoration, preparing bow and arrow for hunt, Northern Cameroon, West Africa. No release available.

Edwin Giesbers / Male Sulawesi red-knobbed hornbill (Aceros cassidix) head portrait, captive

Tim Laman / Rhinoceros hornbill (Buceros rhinoceros) perched in tree, Gunung Palung National Park, West Kalimantan, Borneo, Indonesia.

Tim Laman / Rufous-necked hornbill (Aceros nipalensis) perched on branch, Huai Kha Khaeng Wildlife Sanctuary, Thailand. IUCN Vulnerable

Tim Laman / Various seeds of rainforest trees regurgitated by Rufous-necked Hornbill (Aceros nipalensis). Huai Kha Khaeng Wildlife Sanctuary, Thailand.

Tim Laman / Female Knobbed hornbill (Aceros cassidix) in flight. Tangkoko Batuangus / Dua Saudara Nature Reserve, Sulawesi Island, Indonesia.

Tim Laman / Great indian hornbill (Buceros bicornis) male brings food to nest, Khao Yai National Park, Thailand

Eric Baccega / Head portrait of Papuan hornbill (Aceros plicatus rhyticeros) captive, from SE Asia