Staffan Widstrand / Raven (Corvus corax) mobbing Gyrfalcon (Falco rusticolus), Hornoya Island, Varanger Peninsula, Norway, March.

Ingo Arndt / Osprey (Pandion haliaetus) carrying stick to build nest and mobbed by American Crow (Corvus brachyrhynchos), Sanibel Island, Florida, USA, January.

Staffan Widstrand / Raven (Corvus corax) mobbing Gyrfalcon (Falco rusticolus), Hornoya Island, Varanger Peninsula, Norway, March.

David Pattyn / Common raven (Corvus corax) flying, Hornoya, Varanger, Finnmark, Norway, May.

David Pattyn / Common raven (Corvus corax) fighting in flight, Hornoya, Varanger, Finnmark, Norway, May.

David Pattyn / Common Raven (Corvus corax) flying with egg stolen from Kittiwake nest, Hornoya, Varanger, Finnmark, Norway, May.

Brent Stephenson / Juvenile Eurasian Jackdaw (Corvus monedula) begging to be fed with beak wide open. Visby, Gotland Island, Sweden. June.

Brent Stephenson / Eurasian Jackdaw (Corvus monedula) standing on the edge of a pond in an urban park. Visby, Gotland Island, Sweden. June.

Andy Trowbridge / North Island Kokako (Callaeas wilsoni) perched in tree (Coprosma species), showing diagnostic blue fleshy wattles. Tiritiri Matangi Island, Auckland, New Zealand. September. ENDANGERED SPECIES.

Brent Stephenson / Adult female Kokako (Callaeas wilsoni) perched in a shrub showing the distinctive strong legs, black zoro mask and blue wattles of this species. Tiritiri Matangi Island, Auckland, New Zealand, October...

Brent Stephenson / Adult kokako (Callaeas wilsoni) perched in a flowering Pohutukawa tree (Metrosideros excelsa) and feeding on nectar. Tiritiri Matangi Island, Auckland, New Zealand, December. Endangered species.

Tui De Roy / North Island Kokako (Callaeas cinerea wilsoni) singing. Otorohanga Breeding Centre, New Zealand.

Tui De Roy / North Island Kokako (Callaeas cinerea wilsoni) Otorohonga Breeding Centre, New Zealand.

Tui De Roy / North Island Kokako (Callaeas cinerea wilsoni) Otorohanga Breeding Centre, New Zealand.

Kevin Schafer / Palm Crow (Corvus palmarum) displaying in tree tops, Goat Island, Lago Enriquillo National Park, Dominican Republic

Kevin Schafer / Palm Crow (Corvus palmarum) calling on cactus, Goat Island, Lago Enriquillo National Park, Dominican Republic

Steve Gettle / Ring-necked Duck (Aythya collaris) pair, Crow Island State Game Area, Michigan

Matthew Maran / An American Bald Eagle (Haliaeetus leucocephalus) with remains of fish prey while a crow waits for scraps. Ucluelet, Vancouver Island, Canada, June.

Matthias Breiter / Common Raven (Corvus corax) pair flying along the slopes of Mount Warburton Pike overlooking Boundary Pass, Saturna Island, British Columbia, Canada

Suzi Eszterhas / Common Raven (Corvus corax), San Benito Island, Baja California, Mexico

Suzi Eszterhas / Common Raven (Corvus corax) flying, San Benito Island, Baja California, Mexico

Suzi Eszterhas / Common Raven (Corvus corax) flying, San Benito Island, Baja California, Mexico

Tui De Roy / Common Raven (Corvus corax) perching in Cardon cactus (Pachycereus pringlei), Sonoran Desert, Santa Catalina Island, Sea of Cortez, Baja California, Mexico

Frederique Olivier / American crow (Corvus brachyrhynchos) and flock of Iceland gulls (Larus glaucoides) feeding on remains of carcass of Narwhal (Monodon monoceros) left by hunters, Baffin Island, Canada.

Frederique Olivier / American crow (Corvus brachyrhynchos) and flock of Iceland gulls (Larus glaucoides) feeding on remains of carcass of Narwhal (Monodon monoceros) left by hunters, Baffin Island, Canada.

Bruce Thomson / North Island kokako (Callaeas wilsoni) in leafy branches, critically endangered almost flightless bird, Tiritiri Matangi Island, North Island, New Zealand.