The lake duck (''Oxyura vittata'') is a small,

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...

n stiff-tailed duck. It is also called the Argentine blue-bill, Argentine blue-billed duck, Argentine lake duck, or Argentine ruddy duck.

Description

The lake duck grows to . Females weigh and males . Males can be distinguished from

Andean duck The Andean duck (''Oxyura ferruginea'') is a bird species native to the Andean Mountains of South America, one of the stiff-tailed ducks. It was considered a subspecies of the ruddy duck. In fact, some taxonomic authorities still consider it co ...

(''Oxyura ferruginea''), a similar species, by being smaller and having a flatter head. Duck reproduction

Penis

The lake duck holds the

Guinness World Record ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...

for having the largest avian reproductive organ, from a specimen in

Córdoba, Argentina Córdoba () is a city in central Argentina, in the foothills of the Sierras Chicas on the Suquía River, about northwest of Buenos Aires. It is the capital of Córdoba Province and the second most populous city in Argentina after Buenos ...

that had a penis measuring . It also has the longest

penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males d ...

of any

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...

in relation to body length. 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 has a soft tip and spiny base. It is theorized that the 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. The males often try to force

copulation Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetra ...

, but the complex mating geometry allows the females to retain control—most forced copulations do not result in successful fertilization.

Behavior

Little is known about the lake duck's diet, but it is believed to consist of small invertebrates, seeds, and plant remains. The breeding season varies between countries, occurring from October to January in Argentina. Males produce popping noises and "mechanical rustling noises" for display.

Distribution

The lake duck is a partially migratory species. It lives in bodies of freshwater with large amounts of vegetation, such as wetlands and lakes. It is very widespread, naturally occurring in Argentina, Brazil, Chile, Paraguay, and Uruguay, and having been introduced to Antarctica and the

Falkland Islands The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubouze ...

. It has a stable population of 6,700–67,000, with no major threats. As of 2016, it is listed as a species of

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. ...

on the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biolo ...

References

External links

* {{Taxonbar, from=Q646048 Oxyurinae Ducks Birds of Argentina Birds of Chile Birds described in 1860 Taxa named by Rodolfo Amando Philippi