[order] ANSERIFORMES | [family] Anatidae | [latin] Oxyura vittata | [authority] Philippi, 1860 | [UK] Lake Duck | [FR] Erismature orne | [DE] Binden-Ruderente | [ES] Pato zambullidor Chico (Arg), Malvasia Argentina | [NL] Argentijnse Stekelstaart | [copyright picture] Roberto Ares
The stiff-tailed ducks are part of the Oxyurinae subfamily of ducks. All have, as their name implies, long stiff tail feathers, which are erected when the bird is at rest. All have relatively large swollen bills. These are freshwater diving ducks. Their legs are set far back, making them awkward on land, so they rarely leave the water. Their unusual displays involve drumming noises from inflatable throat-sacs, head throwing, and erecting short crests. Plumage sequences are complicated, and aging difficult. Plumage is vital for survival because of this animals tendency to spend time in the water. Without plumage this duck would die of hypothermia because of an inability to regulate its body temperature. A fossil species from the Late Pliocene or Early Pleistocene of Jalisco (Mexico) was described as Oxyura zapatanima. It resembled a small Ruddy Duck or, even more, Argentine Blue-bill. A larger Middle Pleistocene fossil form from the southwestern USA was described as Oxyura bessomi; it was probably quite close to the Ruddy Duck.
Males are handsomely patterned with a chestnut body, black head, and large, blue bill; females are brownish marked with a contrasting pale subocular stripe and throat. The species is remarkable in that the males have the longest penis relative to body size of any bird; the organ has apparently evolved a brush-like tip to remove sperm from previous matings.
Listen to the sound of Lake Duck
Copyright remark: Most sounds derived from xeno-canto
recorded by Bernabe Lopez-Lanus
South America : Southern Cone. Much of Chile and Argentina, northward to south-eastern Brazil and southward to Tierra del Fuego.
Prefers pools, marshes and shallow lakes with extensive emergent vegetation. Larger lakes and lagoons outside breeding season.
Breefing starts begin October, usually solitery pairs or loose groups. Nest is built in dense vegetation, a flat platform over water. Clutch size is 3-5 eggs which are incubated for about 23-28 days by female. The males usually abandon mate during this period. It wil however defend female during laying. Young are tended by female only, they fledge after 8-9 weeks.
Dives for food on bottom of water. Forages for seeds, plant remains and small invertebrates.
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.
Southern populations migrate to lower latitudes in the winter, moving north to Central Brazil, Uruguay and Paraguay. Other populations are mainly sedentary except in severe drought.