Falaropo di Wilson

Identificazione

Wilson's phalarope is slightly larger than the red phalarope at about 23 cm (9.1 in) in length. It is a dainty shorebird with lobed toes and a straight fine black bill. The breeding female is predominantly gray and brown above, with white underparts, a reddish neck and reddish flank patches. The breeding male is a duller version of the female, with a brown back, and the reddish patches reduced or absent.<p>Measurements:<p>In a study of breeding phalaropes in the province of Saskatchewan, Canada, females were found to average around 10% larger in standard measurements and to weigh around 30% more than the males. Females weighed from 68 to 79 g (2.4 to 2.8 oz), whereas males average 51.8 g (1.83 oz).<p>Young birds are grey and brown above, with whitish underparts and a dark patch through the eye. In winter, the plumage is essentially grey above and white below, but the dark eyepatch is always present. The average longevity in the wild is 10 years.

Tassonomia

Nome scientifico

Phalaropus tricolor

Autorità

(Vieillot, 1819)

Ordine

Caradriformi

Famiglia

Scolopacidi

Genere

Phalaropus

Areale e habitat

Areale riproduttivo

NA : temperate zone inland marshes of Nearctic: w, c Canada and nw to wc USA

Areale non riproduttivo

to hypersaline lakes of w Canada and USA for molt migration; then mainly saline montane lakes from Peru to Argentina; also w coast of South America from Ecuador s and Argentina to Tierra del Fuego

Migrazione

Complete migrants

Comportamento

Wilson's phalaropes are unusually halophilic (salt-loving) and feed in great numbers when on migration on saline lakes such as Mono Lake in California, Lake Abert in Oregon, and the Great Salt Lake of Utah, often with red-necked phalaropes.<p>When feeding, a Wilson's phalarope will often swim in a small, rapid circle, forming a small whirlpool. This behaviour is thought to aid feeding by raising food from the bottom of shallow water. The bird will reach into the outskirts of the vortex with its bill, plucking small insects or crustaceans caught up therein.<p>The typical avian sex roles are reversed in the three phalarope species. Females are larger and more brightly coloured than males. The females pursue males, compete for nesting territory, and will aggressively defend their nests and chosen mates. Once the females lay their eggs, they begin their southward migration, leaving the males to incubate the eggs. Three to four eggs are laid in a ground nest near water. The young feed themselves.<p>Although very common, this bird's population may have declined in some areas due to the loss of prairie wetland habitat. A few staging areas are of critical importance during migration.

Conservazione

Tendenza della popolazione

rising