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Identificazione

The bufflehead ranges from 32–40 cm (13–16 in) long and weighs 270–550 g (9.5–19.4 oz), with the drakes larger than the females. Averaging 35.5 cm (14.0 in) and 370 g (13 oz), it rivals the green-winged teal as the smallest American duck. The bufflehead has a wingspan of 21.6 in (55 cm).<p>Adult males are striking black and white, with iridescent green and purple heads and a large white patch behind the eye. Females are grey-toned with a smaller white patch behind the eye and a light underside.

Tassonomia

Nome scientifico

Bucephala albeola

Autorità

(Linnaeus, 1758)

Ordine

Anseriformi

Famiglia

Anatidae

Genere

Bucephala

Areale e habitat

They are migratory and most of them winter in protected coastal waters, or open inland waters, on the east and west coasts of North America and the southern United States. They can also be observed wintering on the Great Lakes. The bufflehead is an extremely rare vagrant to western Europe. Their breeding habitat is wooded lakes and ponds in Alaska and Canada, almost entirely included in the boreal forest or taiga habitat. From 1966 - 2015, the bufflehead experienced a &gt;1.5% yearly population increase throughout its breeding range.

Areale riproduttivo

NA : subarctic wc Alaska and Canada e to e Quebec and (locally) nw, nc USA

Areale non riproduttivo

to c Mexico and n Florida

Migrazione

Complete migrants

Comportamento

Buffleheads have evolved their small size to fit the nesting cavity of their "metabiotic" host, a woodpecker, the northern flicker. Due to their small size, they are highly active, undertaking dives almost continuously while sustained by their high metabolism. They do not tend to collect in large flocks; groups are usually limited to small numbers. One duck serves as a sentry, watching for predators as the others in the group dive in search of food. Buffleheads are amongst the last waterfowl to leave their breeding grounds and one of the world's most punctual migrants, arriving on their wintering grounds within a narrow margin of time.<p>Buffleheads are monogamous, and the females may return to the same nest site, year after year. They nest in cavities in trees, primarily aspens or poplars, using mostly old flicker nests, close (usually &lt; 25 m (82 ft)) to water. Nest competitors include mountain bluebird (Sialia currucoides), tree swallow (Tachycineta bicolor), and European starling. There was one recorded instance of a female Barrow's goldeneye killing a bufflehead adult female and her brood. Smaller cavities are preferred because of less competition with the larger goldeneyes. Females may be killed on the nest by mammals, such as foxes (Vulpes and Urocyon sp.), weasels (Mustela and Neogale sp.) or mink (Neogale vison), and by goldeneyes over nest competition.<p>Average clutch size is nine (range six to 11), and eggs average 50.5 by 36.3 mm (1.99 by 1.43 in). Incubation averages 30 days, and nest success is high (79% in one study) compared to ground-nesting species like the teal. A day after the last duckling hatches, the brood leaps from the nest cavity. The young fledge at 50–55 days of age. Predators of adults include the peregrine falcon (Falco peregrinus), snowy owl (Bubo scandiacus), bald eagle (Haliaeetus leucocephalus), golden eagle (Aquila chrysaetos), red-tailed hawk (Buteo jamaicensis), great horned owl (Bubo virginianus), and Cooper's hawk (Accipiter cooperii).<p>These diving birds forage underwater. They prefer water depths of 1.2–4.5 m (3.9–14.8 ft). In freshwater habitats, they eat primarily insects, and in saltwater, they feed predominantly on crustaceans and mollusks. Aquatic plants and fish eggs can often become locally important food items, as well.

Conservazione

Tendenza della popolazione

rising