Nick Saunders/ BIA / Ruddy Duck (Oxyura jamaicensis) male in courtship display, Saskatchewan, Canada

Alan Murphy / Ruddy Duck (Oxyura jamaicensis) male in courtship display, British Columbia, Canada

Alan Williams / Male Ruddy Duck (Oxyura jamaicensis) displaying on lake expelling air from breast feathers to form bubbles (captive bird) UK, May 2010

Gerrit Vyn / Ruddy Duck (Oxyura jamaicensis) male in breeding plumage performing a "bubbling display"which is used in both courtship and aggressive territorial encounters. The male holds its head and tail and 2 ro...

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.

Fabio Pupin / Iberian worm lizard, (Blanus cinereus), emerging from sandy soil, Spain, October . Non-ex.

Fabio Pupin / Iberian worm lizard, (Blanus cinereus), Spain, September . Non-ex.

Fabio Pupin / Iberian worm lizard, (Blanus cinereus), close-up of the head, Spain, September . Non-ex.

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.

Gabriel Rojo / Lake duck, (Oxyura vittata), La Pampa, Patagonia