Terry Whittaker / Mandarin duck (Aix galericulata) male female pair, Reddish Vale Country Park, Greater Manchester, UK. December

Steven David Miller / Eclectus parrot (Eclectus roratus) female perched in a tree, The Wildlife Habitat Zoo, Port Douglas, Queensland, Australia. August. Captive.

Donald M. Jones / Northern Pintail (Anas acuta) males flying with female in spring courtship display, Montana

Donald M. Jones / Bighorn Sheep (Ovis canadensis) female and male in winter, Jasper National Park, Alberta, Canada

Chien Lee / Minden / Stick Insect (Monticomorpha flavolimbata) pair mating in mountains, Bengoh Range, Ecuador

Theo Bosboom / Variable damselfly (Coenagrion pulchellum) pair mating, De Peel National Park, the Netherlands, July.

Donald M. Jones / Bighorn Sheep (Ovis canadensis) ewe and ram, western Montana

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

Michael Quinton / Dall's Sheep (Ovis dalli) ram, lamb, and ewe, Yukon Territory, Canada

Luciano Candisani / Green Anaconda (Eunectes murinus) female constricting male after copulation, after which she will consume him, Brazil

Alan Murphy/ BIA / Northern Bobwhite (Colinus virginianus) female and male, Texas

Bence Mate / Red footed falcon (Falco vespertinus) pair mating, Lake Csaj, Kiskunsagi National Park, Pusztaszer, Hungary. February.