Charlie Summers / Ruddy duck (Oxyura jamaicensis) female rolling on her side as she preens. Image taken on an Arapaho National Wildlife Refuge pond in North Park, Colorado.

Charlie Summers / Ruddy duck (Oxyura jamaicensis) drake making bubbles in courtship behaviour, Arapaho National Wildlife Refuge pond, North Park, Colorado.

Oscar Dewhurst / Crested duck (Lophonetta specularioides) walking on a frozen Andean lake. Arequipa, Peru. September. Cropped

Oscar Dewhurst / Puna teal (Anas puna) standing in shallow water of an Andean lake. Arequipa, Peru. September. Cropped

Oscar Dewhurst / Yellow-billed teal (Anas flavirostris) swimming in Andean lake. Arequipa, Peru. September

John Shaw / Ruddy duck (Oxyura jamaicensis) in a small marsh pond, doing courtship display where it beats its breast with bill to create bubbles. British Columbia, Canada. June.

John Chan / Male Ruddy duck (Oxyura jamaicensis) in winter plumage diving to feed on aquatic plants and insects, Bolsa Chica Ecological Reserve, California, USA, December.

Marie Read / Ruddy Duck (Oxyura jamaicensis) male with tail raised during courtship display (bubble display), Bowdoin National Wildlife Refuge, Montana, USA, June.

Cyril Ruoso / Ruddy duck (Oxyura jamaicensis) male on Lake Titicaca, Bolivia

Cyril Ruoso / Ruddy duck (Oxyura jamaicensis) juvenile on Lake Titicaca, Bolivia

Cyril Ruoso / Ruddy duck (Oxyura jamaicensis) male on Lake Titicaca, Bolivia

Claudio Contreras / Ruddy duck (Oxyura jamaicensis jamaicensi) male in courtship display, Xochimilco wetlands, Mexico City, August