Fistione beccorosa

Identificazione

Like many other members of family Anatidae, the rosy-billed pochard exhibits significant sexual dimorphism. Males have a purplish-black head, neck and breast with gray sides, a white area on the crissum (the area around the cloaca), and a bright red bill and red eyes. The bill has a large rounded knob, which is bright red, and rest of the bill gradually fades towards a pale pink before ending with a black tip. The rounded knob of the bill increases in size and intensity in colour during the mating season. When in flight, the mostly dark plumage noticeably contrasts with the white primaries and secondaries. The legs and feet are yellow to orange. On the other hand, females are dull and brown. The bill is bluish-gray with a black tip and the legs are yellow-orange to gray. The contrasting white crissum is the most noticeable feature on females.<p>Young are almost identical in appearance to the females, but their underparts are darker. Rosybill adults lack the dull eclipse plumage that is characteristic of northern individuals of the genera Aytha and Anas.<p>Males tend to be slightly larger than females, but in general both sexes are very similar in terms of body size. Adults can grow to about 22 inches (56 cm) in length and weigh 2.2-2.6 pounds (1-1.2 kg). Despite these pochards being strong fliers, their blunt-tipped wings require a faster wing-beats than that of many ducks and they have some trouble taking off. They do not walk as well on land as other dabbling ducks because their legs are placed further back on their bodies to help propel them when underwater. Their minimum wingspan recorded is 72 cm, while the maximum is 84 cm.

Tassonomia

The rosy-billed pochard is one of five pochard species that make up the genus Netta, which is one of 31 genera of the subfamily Anatinae. Within subfamily Anatinae, there is a tribe called Aythini. This tribe was thought to be limited to the Northern Hemisphere (what was believed to be the Palearctic), and experienced three or four bursts of speciation, one of which was by the ancestor of the rosy-billed and southern pochards. Rosy-billed pochards were first described in 1816 by taxon author Viellot, in Paraguay and Buenos Aires, Argentina. The species is highly autapomorphic and is placed in a sister-group with the southern pochard, but evidence for this relationship is lacking. Additionally, they have been known to hybridize with the red-crested pochard and other pochards from ornamental waterfowl collections. The rosybill is monotypic and thus no further classifications exist.

Nome scientifico

Netta peposaca

Autorità

(Vieillot, 1816)

Ordine

Anseriformi

Famiglia

Anatidae

Genere

Netta

Areale e habitat

Rosy-billed pochards nest within tall grasses in wetlands, mainly in areas that extend from the central provinces of Córdoba, Santa Fe, Entre Ríos, and Buenos Aires, southwards to Río Negro. Individuals are also found in shallow freshwater swamps, marshes and small lakes.<p>They are a fully migrant species and their movements are heavily associated with water conditions. Seasonal dry periods are common in central Argentina and they force birds to move towards larger water areas in late summer. By early fall, these areas are often dry and individuals are forced to move to find more water and better food sources elsewhere. An increase in population size can be seen during wet periods.

Migrazione

Migratori completi

Comportamento

Comportamento migratorio: Migratori completi.

Conservazione

Tendenza della popolazione: in aumento.

Tendenza della popolazione

in aumento