Lake duck / Argentine ruddy duck

Oxyura vittata

Argentijnse stekelstaart / Arg. Ruderente / Erismature d'Argentine

The lake duck (Oxyura vittata) is a small, South American stiff-tailed duck. It is also called the Argentine blue-bill, Argentine lake duck, or Argentine ruddy duck. The lake duck lives in Argentina, Brazil, Chile, Paraguay and Uruguay in southern South America.

It is notable for possessing, in relation to body length, the longest penis of all vertebrates; the penis, which is typically coiled up in flaccid state, can reach about the same length as the animal itself when fully erect, but more commonly is about half the bird's length. It is theorized that the remarkable size of their spiny penises with bristled tips may have evolved in response to competitive pressure in these highly promiscuous birds, removing sperm from previous matings in the manner of a bottle brush.

Although most male birds have no penis, ducks have a long corkscrew penis, and the females have a long corkscrew vagina, which spirals in the opposite direction. Scientists have suggested that males use their penises to lasso reluctant females. The males often try to force copulation, but the complex mating geometry allows the females to retain control—most forced copulations do not result in successful fertilization.

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern by the IUCN.

More information: http://www.iucnredlist.org/details/100600361/0

Ringsize for captive bred birds: 9mm

Above: male Argentine ruddy ducks/ Lake ducks

Above: male Argentine ruddy ducks/ Lake ducks (eclipse birds)

Above: male Argentine ruddy duck/ Lake duck

Above: male Argentine ruddy duck/ Lake duck

Above: two males en one female (background) Argentine ruddy duck/ Lake duck

Above: male Argentine ruddy duck/ Lake duck

Above: male Argentine ruddy duck/ Lake duck

Above: male Argentine ruddy duck/ Lake duck

Above: Close-ups of Stiff-tailed ducks (genus Oxyura) for identification. Click to enlarge.