Glenn Bartley / Arctic Skua (Stercorarius parasiticus) flying, Manitoba, Canada

Glenn Bartley / Arctic Skua (Stercorarius parasiticus), Manitoba, Canada

Tim Laman / South polar skua (Catharacta maccormicki) feeding on dead Gentoo penguin, Cuverville Island, Ererra Channel, Gerlache Strait vicinity, Antarctica.

Winfried Wisniewski / Arctic Skua (Stercorarius parasiticus) dark morph flying, Flatanger, Norway

Winfried Wisniewski / Arctic Skua (Stercorarius parasiticus) dark morph flying, Flatanger, Norway

Winfried Wisniewski / Arctic Skua (Stercorarius parasiticus) light morph, Varangerfjord, Norway

Winfried Wisniewski / Arctic Skua (Stercorarius parasiticus) dark morph flying, Flatanger, Norway

Winfried Wisniewski / Arctic Skua (Stercorarius parasiticus) dark morph flying, Flatanger, Norway

Winfried Wisniewski / Arctic Skua (Stercorarius parasiticus) dark morph, Flatanger, Norway

Winfried Wisniewski / Long-tailed Jaeger (Stercorarius longicaudus) light morph, Varanger Peninsula, Norway

Ben Cranke / Arctic skua (Stercorarius parasiticus) Svalbard, Norway. July.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) in flight. Handa Island, Scotland, UK. June.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) calling in flight. Handa Island, Scotland, UK. June.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) in flight. Handa Island, Scotland, UK. June.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) calling and coming in to land. Handa Island, Scotland, UK. June.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) group on water. Handa Island, Scotland, UK. June.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) pair bonding and calling in defence of territory. Handa Island, Scotland, UK. June.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) stretching. Handa Island, Scotland, UK. June.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) stretching. Handa Island, Scotland, UK. June.

Sam Hobson / Great skuas or 'bonxies' (Stercorarius skua / Catharacta skua) fighting over territory. Handa Island, Scotland, UK. June.

Sam Hobson / Great skuas or 'bonxies' (Stercorarius skua / Catharacta skua) fighting over territory. Handa Island, Scotland, UK. June.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) calling in defence of territory. Handa Island, Scotland, UK. June.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) perched on lichen covered rock. Handa Island, Scotland, UK. June.

Sam Hobson / Great skua or 'bonxie' (Stercorarius skua / Catharacta skua) with mountains in distance. Handa Island, Scotland, UK. June.

David Tipling / Great Skuas (Stercorarius skua) Unst, Shetland, Scotland, UK, June.

David Tipling / Arctic Tern (Sterna paradisaea) chasing off Arctic Skua (Stercorarius parasiticus) near colony on, Shetland, Scotland, UK, June.

David Tipling / Great Skus (Stercorarius skua) fighting in territorial dispute Hermaness, Unst, Shetland, Scotland, UK. June.

David Tipling / Arctic Skua (Stercorarius parasiticus) chick, Fair Isle, Scotland, UK.

Markus Varesvuo / Long-tailed Skua (Stercorarius longicaudus) portrait, June, Norway

Markus Varesvuo / Long-tailed Skua (Stercorarius longicaudus)foraging on icesheet, Norway

Markus Varesvuo / Long-tailed Skua (Stercorarius longicaudus) back-lit, with wings outstretched, Utsjoki July, Finland,

Markus Varesvuo / Long-tailed Skua (Stercorarius longicaudus) flying low over snow, June, Norway

Markus Varesvuo / Long-tailed Skua (Stercorarius longicaudus) in flight, June, Norway

Markus Varesvuo / Long-tailed Skua (Stercorarius longicaudus) foraging on ice, June, Norway, Europe

Markus Varesvuo / Great skua (Catharacta / Stercorarius skua) in flight carrying dead Tern (Sterna sp) Iceland, June

Markus Varesvuo / Arctic skua (Stercorarius parasiticus) in flight, calling, Norway, July

Markus Varesvuo / Arctic Skua (Stercorarius parasiticus) in flight, Norway, August

Markus Varesvuo / Arctic Skua (Stercorarius parasiticus) perched, Norway, July

Markus Varesvuo / Arctic Skua (Stercorarius parasiticus) in flight, Norway, July

Markus Varesvuo / Long-tailed Skua (Stercorarius longicaudus) flying, Utsjoki, Finland, July

Markus Varesvuo / Long-tailed Skua (Stercorarius longicaudus) calling while flying, Utsjoki, Finland, July

Markus Varesvuo / Long-tailed Skua (Stercorarius longicaudus) Norway July

Markus Varesvuo / Long-tailed Skua (Stercorarius longicaudus) flying, Norway, June

Markus Varesvuo / Arctic Skua (Stercorarius parasiticus) dark phase, in flight, Norway June

Markus Varesvuo / Arctic Skua (Stercorarius parasiticus) Eggs , Norway June on ground

Markus Varesvuo / Arctic Skua (Stercorarius parasiticus) dark phase, Norway June

Markus Varesvuo / Arctic Skua (Stercorarius parasiticus) flying, Norway June

Markus Varesvuo / Arctic Skua (Stercorarius parasiticus), Norway June

Markus Varesvuo / Great Skua (Catharacta skua) flying wtih dead Arctic Tern prey (Sterna paradisaea), Iceland June

Markus Varesvuo / Great Skua (Catharacta / Stercorarius skua) feeding on dead gull, Iceland.

Markus Varesvuo / Great Skua (Stercorarius skua) flying with dead gull / tern prey, Iceland. Magic Moments book plate.

Erlend Haarberg / Great skuas (Catharacta skua) calling, Norway. July.

Pal Hermansen / Arctic skua (Stercorarius parasiticus) in flight, Hotellneset, Svalbard, Norway. July.

Pal Hermansen / Ivory gull (Pagophila eburnea) and Arctic skua (Stercorarius parasitcus) over ice, Franz Josef land, Arctic Russia, July.

Pal Hermansen / Arctic Skua (Stercorarius parasiticus) in flight, Hotellneset, Svalbard, Norway, July.

Roy Mangersnes / Long-tailed skua (Stercorarius longicaudus) portrait, on ice, Spitsbergen, Svalbard, Norway, June.

David Tipling / Great Skua (Stercorarius skua) pair at nest in late evening at Hermaness, Unst, Shetland, Scotland, UK, June.

Frederique Olivier / Emperor penguin (Aptenodytes forsteri) adults and chicks resting on their way to the sea with South Polar skua (Stercorarius maccormicki) keeping watch, Antarctica, December.

Brent Stephenson / Adult light morph Pomarine jaeger (Stercorarius pomarinus) in breeding plumage with large tail 'spoons'. Cape St Elias, Alaska, United States. July.

Brent Stephenson / Adult South Polar skua (Catharacta maccormicki) with worn plumage, in flight against a grey sky. Off the Three Kings, Far North, New Zealand, April.

Sergey Gorshkov / Long-tailed jaegers (Stercorarius longicaudus) mobbing Arctic fox (Vulpes lagopus) Wrangel Island, Far Eastern Russia, June.

Andy Trowbridge / Great skua (Stercorarius skua) standing on stone fence giving a territorial display. Mousa Island, Shetland, Scotland, UK. July.

Terry Whittaker / Light phase Arctic skua (Stercorarius parasiticus) calling, Jokulsarlon, Vatnajokull Glacier, Iceland, July.

Russell Laman / South Polar Skua (Stercorarius maccormicki) portrait, Antarctica, February.

Roland Seitre / Sculpture of Skua egg (Stercorarius parasiticus) 'Eggin i Gledivik?' by Siguraur Guamundsson, ?34 giant granite eggs along the coast? at Djupivogur, Iceland, June 2011.

Filippo Nucifora / Long-tailed Jaeger (Stercorarius longicaudus), Switzerland

Jussi Murtosaari / Long-tailed Jaeger (Stercorarius longicaudus) resting on rock in habitat, Finland, July.

Jussi Murtosaari / Long-tailed Jaeger (Stercorarius longicaudus) resting on rock in habitat, Karigasniemi, Finland, July.

Jussi Murtosaari / Arctic skua (Stercorarius parasiticus) in flight, Norway, June.

Jussi Murtosaari / Arctic skua (Stercorarius parasiticus) light and dark forms, Norway, June.

Jussi Murtosaari / Long-tailed Jaeger (Stercorarius longicaudus) adult, Lapland, Finland, June.

Roger Powell / Dark phase male Arctic Skua (Sterocorarius parasiticus) shuffling feathers after preening. Varanger, Finmark, Norway, May.

Roger Powell / Pair of Arctic Skuas (Stercorarius parasiticus) dark phase male and light phase female. Varanger, Finmark, Norway

Roger Powell / Male dark phase Arctic Skua (Stercorarius parasiticus) courtship feeding light phase female. Varanger, Finmark, Norway, May.

Christophe Courteau / Arctic skua (Stercorarius parasiticus) with fish prey, Spitzbergen, Svalbad, Norway, June.

Christophe Courteau / Arctic skua (Stercorarius parasiticus) stealing a fish from a Kittiwake (Rissa tridactyla), Spitzbergen, Svalbad, Norway, June.

Christophe Courteau / Arctic skua (Stercorarius parasiticus) stealing a fish from a Kittiwake (Rissa tridactyla), Spitzbergen, Svalbad, Norway, June.

Christophe Courteau / Arctic skua (Stercorarius parasiticus) in flight, Spitzbergen, Svalbad, Norway, June.

Ralph Martin / Arctic Skua (Stercorarius parasiticus), Baden-Wurttemberg, Germany

Ralph Martin / Arctic Skua (Stercorarius parasiticus), Baden-Wurttemberg, Germany

Alan Murphy / Long-tailed Jaeger (Stercorarius longicaudus), Alaska

Alan Murphy / Long-tailed Jaeger (Stercorarius longicaudus), Alaska

Glenn Bartley / Arctic Skua (Stercorarius parasiticus), Manitoba, Canada

Glenn Bartley / Arctic Skua (Stercorarius parasiticus), Manitoba, Canada

Jacob S. Spendelow / Pomarine Jaeger (Stercorarius pomarinus), Alaska

Jacob S. Spendelow / Long-tailed Jaeger (Stercorarius longicaudus), Alaska

Jacob S. Spendelow / Long-tailed Jaeger (Stercorarius longicaudus), Alaska

Alan Murphy / Arctic Skua (Stercorarius parasiticus) flying, Alaska

Alan Murphy / Pomarine Jaeger (Stercorarius pomarinus) flying, Alaska

Michael Quinton / Long-tailed Jaeger (Stercorarius longicaudus), Brooks Range, Alaska

Enrique Lopez-Tapia / Subantarctic Skua (Catharacta antarctica) on snow, Danco Island. Antarctic Peninsula, Antarctica

Ben Cranke / Gentoo Penguins (Pygoscelis papua) at nesting colony showing defensive behaviour to Antarctic skua (Stercorarius antarcticus) Cuverville Island, Antarctic Peninsula, Antarctica. Panoramic composite

Ben Cranke / Gentoo Penguin (Pygoscelis papua) showing defensive display at Antarctic skua (Stercorarius antarcticus) Cuverville Island, Antarctic Peninsula, Antarctica

Ben Cranke / Gentoo Penguins (Pygoscelis papua) watching Antarctic skua (Stercorarius antarcticus) Cuverville Island, Antarctic Peninsula, Antarctica

Sergey Gorshkov / Long-tailed Jaeger (Stercorarius longicaudus) flying over intruding Arctic Fox (Alopex lagopus) near its nest, Wrangel Island, Russia

Sergey Gorshkov / Arctic Fox (Alopex lagopus) running with a stolen Long-tailed Jaeger (Stercorarius parasiticus) egg in its mouth, Wrangel Island, Russia