Marzaiola americana

Identificazione

The blue-winged teal is 40 cm (16 in) long, with a wingspan of 58 cm (23 in), and a weight of 370 g (13 oz). The adult male has a greyish blue head with a white facial crescent, a light brown body with a white patch near the rear and a black tail. The adult female is mottled brown, and has a whitish area at base of bill. Both sexes have sky-blue wing coverts, a green speculum, and yellow legs. They have two molts per year and a third molt in their first year. The call of the male is a short whistle; the female's call is a soft quack.

Tassonomia

The first formal description of the blue-winged teal was by the Swedish naturalist Carl Linnaeus in 1766 in the twelfth edition of his Systema Naturae. He coined the binomial name Anas discors. A molecular phylogentic study comparing mitochondrial DNA sequences published in 2009 found that the genus Anas, as then defined, was non-monophyletic. The genus was subsequently split into four monophyletic genera with ten species including the blue-winged teal moved into the resurrected genus Spatula. This genus had been originally proposed by the German zoologist Friedrich Boie in 1822. The name Spatula is the Latin for a "spoon" or "spatula". The specific epithet discors is the Latin for "different" or "at variance".

Nome scientifico

Spatula discors

Autorità

(Linnaeus, 1766)

Ordine

Anseriformi

Famiglia

Anatidae

Genere

Spatula

Areale e habitat

The range is all of North America except western and northern Alaska, northern Yukon Territory, northern Northwest Territories and the northeastern area of Canada. Blue-winged teal are rare in the desert southwest, and the west coast. The breeding habitat of the blue-winged teal is marshes and ponds.<p>The breeding range extends from east-central Alaska and southern Mackenzie District east to southern Quebec and southwestern Newfoundland. In the contiguous United States it breeds from northeast California east to central Louisiana, central Tennessee, and the Atlantic Coast. The western blue-winged teal inhabits that part of the breeding range west of the Appalachian Mountains. Some populations of blue-winged teals nest along the Atlantic Coast from New Brunswick to Pea Island, North Carolina.<p>They migrate in flocks to winter in to the south of its breeding range. During migration, some birds may fly long distances over open ocean. They are occasional vagrants to Europe, where their yellow legs are a distinction from other small ducks like the common teal and garganey, and in recent years have been annual vagrants in Britain and Ireland. The blue-winged teal winters from southern California to western and southern Texas, the Gulf Coast to the Atlantic Coast, the Caribbean, and south to Central and South America. It is often seen wintering as far south as Brazil and central Chile. Blue-winged teal inhabit shoreline more often than open water and prefer calm water or sluggish currents to fast water. They inhabit inland marshes, lakes, ponds, pools, and shallow streams with dense emergent vegetation. In coastal areas, breeding occurs in salt-marsh meadows with adjoining ponds or creeks. Blue-winged teal use rocks protruding above water, muskrat houses, trunks or limbs of fallen trees, bare stretches of shoreline, or mud flats for resting sites.<p>Blue-winged teal winter on shallow inland freshwater marshes and brackish and saltwater marshes. They build their nests on dry ground in grassy sites such as bluegrass meadows, hayfields, and sedge meadows. They will also nest in areas with very short, sparse vegetation. Blue-winged teal generally nest within several hundred yards of open water; however, nests have been found as far as 1.61 km (1 mi) away from water. Where the habitat is good, they nest communally.<p>Blue-winged teal often use heavy growth of bulrushes and cattails as escape cover. Grasses, sedges, and hayfields provide nesting cover for these ducks. Erik Fritzell reported that blue-winged teal nests located in light to sparse cover were more successful than those in heavy cover. Nesting success was 47% on grazed areas and 14% on ungrazed areas.<p>The blue-winged teal is primarily found in the northern prairies and parklands. It is the most abundant duck in the mixed-grass prairies of the Dakotas and the prairie provinces of Canada. The blue-winged teal is also found in wetlands of boreal forest associations, shortgrass prairies, tallgrass prairies, and deciduous woodlands.<p>This duck commonly inhabits wetland communities dominated by bulrush (Scirpus spp.), cattail (Typha spp.), pondweed (Potamogeton spp.), sedges (Carex spp.), widgeongrass (Ruppia maritima), and other emergent and aquatic vegetation. During molting, it often remains among extensive beds of bulrushes and cattails. The blue-winged teal favors areas dominated by bluegrass (Poa spp.) for nesting. Hayfields and plant communities of buckbrush (Ceonothus cuneatus) and sedges are also important as nest sites.

Areale riproduttivo

NA : s Canada and USA

Areale non riproduttivo

America media e America meridionale settentrionale

Migrazione

Migratori completi

Comportamento

Comportamento migratorio: Migratori completi.

Conservazione

Tendenza della popolazione: in aumento.

Tendenza della popolazione

in aumento