Bécasseau variable

Identification

Measurements:<p>An adult dunlin in breeding plumage shows the distinctive black belly which no other similar-sized wader possesses. The winter dunlin is basically grey above and white below. Juveniles are brown above with two whitish "V" shapes on the back. They usually have black marks on the flanks or belly and show a strong white wingbar in flight. The legs and slightly decurved bill are black. There are a number of subspecies differing mainly in the extent of rufous colouration in the breeding plumage and the bill length. Bill length varies between sexes, the females having longer bills than the males. On the tip of the Dunlin's bill is a soft covering that fills with blood and with many nerve endings, forming a sensitive probe that is used to locate invertebrate prey in mud and sand. Although the bill can look sharp-pointed in dead specimens, in life it is blunt.<p>The call is a typical sandpiper "peep", and the display song a harsh trill.

Taxonomie

The dunlin was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Tringa alpina. Linnaeus specified the location as Lapland. This species was formerly placed in the genus Erolia, but is now placed with 23 other sandpipers in the genus Calidris that was introduced in 1804 by the German naturalist Blasius Merrem. The genus name is from Ancient Greek kalidris or skalidris, a term used by Aristotle for some grey-coloured waterside birds. The specific alpina is from Latin and means "of high mountains", in this case referring to the Alps.<p>Ten subspecies are recognised:

Nom scientifique

Calidris alpina

Autorité

(Linnaeus, 1758)

Ordre

Charadriiformes

Famille

Scolopacidés

Genre

Calidris

Répartition et habitat

Dunlin are small migratory waders, however they show strong philopatry with individuals of the Southern Dunlin (Calidris alpina schinzii) in Sweden and Finland returning to, or very close to, their natal patches. Habitat fragmentation has reduced the availability of habitat patches to these birds through reducing patch size and increasing patch isolation. This reduced connectivity between patches has reduced the movements of Dunlin leaving them more susceptible to inbreeding in these locations.

Aire de reproduction

NA, PAL : low (locally high) Arctic to temperate wet tundra of Holarctic: sw to ne Greenland, Iceland, Faroe Is., n British Is., Scandinavia, Baltic states e through n Russia including Novaya Zemlya (n of nw Siberia) and New Siberian Is. (n of ec Russia), through Chukotskiy Pen., w Kamchatka, n Kurile and n Sakhalin is. (e Russia); Aleutian Is., w, n Alaska, nw Canada, nc Canada n and w of Hudson Bay

Aire hors reproduction

s NA, AF, s PAL : coastal and inland wetlands from temperate to tropical zones n of Equator: British Is., w Europe, Mediterranean, n, nc Africa, Middle East, n Indian subcontinent to n Vietnam and e China, Taiwan, Korean Pen. and Japan (except n); sw Canada and New England to wc Mexico and Yucatan Pen.

Migration

Complete migrants

Comportement

The dunlin is highly gregarious in winter, sometimes forming large flocks on coastal mudflats or sandy beaches. Large numbers can often be seen swirling in synchronized flight on stop-overs during migration or on their winter habitat.<p>This bird is one of the most common waders throughout its breeding and wintering ranges, and it is the species with which other waders tend to be compared. At 17–21 cm (6.7–8.3 in) length and with a 32–36 cm (13–14 in) wingspan, it is similar in size to a common starling, but stouter, with a thicker bill.<p>The dunlin moves along the coastal mudflat beaches it prefers with a characteristic "sewing machine" feeding action, methodically picking small food items. Insects form the main part of the dunlin's diet on the nesting grounds; it eats molluscs, worms and crustaceans in coastal areas.<p>The nest is a shallow scrape on the ground lined with vegetation, into which typically four eggs are laid and incubated by the male and female parents. Chicks are precocial, but are brooded during early development. They start to fly at approximately three weeks of age. The majority of brood care is provided by the male, as the female deserts the brood and often leaves the breeding area.<p>Apparent hybrids between this species and the white-rumped sandpiper as well as with the purple sandpiper have been reported from the Atlantic coasts of North America and Europe, respectively.

Conservation

Tendance de la population

declining