Stefan Christmann / Emperor penguin (Aptenodytes forsteri) breeding colony, mainly males brooding eggs, huddled together on sea ice. Atka Bay, Antarctica. June.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) breeding colony, adults brooding chicks. Atka Bay, Antarctica. September 2017.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri), two chicks aged six to eight weeks huddling together. Atka Bay, Antarctica. September.

Jack Dykinga / Burrowing owl (Athene cunicularia), two huddled together. Marana, Pima County, Arizona, USA.

Jussi Murtosaari / Blackcap (Sylvia atricapilla) female and two males huddling together for warmth while sleeping, Finland, May.

Frederique Olivier / Close-up of a group of Emperor penguin (Aptenodytes forsteri) chicks huddled together in a blizzard, covered in snow, Adelie Land, Antarctica, January.

Frederique Olivier / Emperor penguin (Aptenodytes forsteri) chicks huddled together during a blizzard, Adelie Land, Antarctica, January.

Konrad Wothe / Chimpanzee (Pan troglodytes) sitting in the rain, Mahale Mountains National Park, Tanzania.

Rosl Roessner/ BIA / Guira Cuckoo (Guira guira) group huddled together, native to South America

Cyril Ruoso / Golden monkey (Rhinopithecus roxellana) females sitting close together with baby inbetween, Qinling Mountains, China.

Markus Varesvuo / Capercaillie (Tetrao urogallus) chicks huddled together, Kuhmo, Finland, June.

Tui De Roy / Little blue / fairy penguin (Eudyptula minor) walking on pathway to nesting burrows, Neck Game Reserve, Bruny Island, Tasmania, Australia, December.