Ismaele Tortella / Three Rock ptarmigan (Lagopus muta) feeding in winter plumage, city of Tromso in the background, northern Norway, March 2019.

Chris Gomersall / Large flock of Red knot (Calidris canutus) moving at high tide roost, in winter plumage, Snettisham RSPB Reserve, Norfolk, England, UK, September.

David Pattyn / Black necked grebe (Podiceps nigricollis) portrait of an adult bird in winter plumage. The Netherlands. April 2014

Markus Varesvuo / Female Black grouse (Tetrao / Lyrurus tetrix) perched in tree covered in snow, Inari Kiilopaa, Finland, January.

Markus Varesvuo / Willow grouse / Ptarmigan (Lagopus lagopus) fluffed up perched in snow, Inari, Finland, February.

Markus Varesvuo / Willow grouse (lagopus lagopus) flock in flight in snow, Utsjoki, Finland, October.

Markus Varesvuo / Willow grouse / Ptarmigan (Lagopus lagopus) flying, Inari Kiilopaa, Finland, February.

Donald M. Jones / Willow Ptarmigan (Lagopus lagopus) trio in fall, transitioning to winter plummage, central Alaska

Danny Green / White tailed eagle (Haliaeetus albicilla) in flight with snowy background, Rausu, Japan, February

Danny Green / Steller's sea eagle (Haliaeetus pelagicus) on snowy ground, Japan, February

Danny Green / Steller's sea eagle (Haliaeetus pelagicus) close up portrait, Japan, February

Danny Green / Japanese crane (Grus japonensis) displaying, wings in heart shape, Hokkaido, Japan, February