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 flying, Flatanger, Norway

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

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

Brent Stephenson / Dark morph adult Kermadec petrel (Pterodroma neglecta) at a nest on the surface of the ground. Meyer Islets, Kermadec Islands, New Zealand, November.

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

Paul Hobson / Common Marbled Carpet (Chloroclysta truncata) dark morph, resting on wood, Sheffield

Bertie Gregory / Vancouver Island Grey wolf (Canis lupus crassodon) dark morph and light morph, Vancouver Island, British Columbia, Canada.

Bertie Gregory / Vancouver Island Grey wolf (Canis lupus crassodon) dark morph and light morph, Vancouver Island, British Columbia, Canada.

Bertie Gregory / Vancouver Island Grey wolf (Canis lupus crassodon) dark morph Vancouver Island, British Columbia, Canada.

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