This small shorebird is distinctive in breeding plumage, with a black belly-patch extending behind its black legs. Its head and breast are light-colored, and its back is bright rufous. In non-breeding plumage it is drab gray with a brownish head and breast. In flight it has white underwings, a white line down the middle of the upperwing, and white on either side of its rump and tail. The white underwings are especially distinctive in flight. As a flock twists and turns together in flight, white flashes of underwing are evident from a distance.
Dunlin flocks are often huge, most impressive when they display their coordinated aerial maneuvers trying to escape predation by Peregrine Falcons and Merlins. When foraging, they either pick food from the surface or probe in the mud. They feed on exposed mud or in shallow water, making short runs interspersed with periods of feeding. They feed day or night, depending on the timing of low tide.
Tundra-breeders, Dunlin typically nest in wet meadow tundra with low ridges, vegetation hummocks, and nearby ponds. During migration and winter, they prefer mudflats, but can also be seen on sandy beaches, coastal grasslands, estuaries, and occasionally in muddy, freshwater areas.
Calidris alpina breeds mainly in northern Europe, which accounts for less than half of its global breeding range. Its European breeding population is large (>300,000 pairs), and was probably stable between 1970-1990 (although the European wintering population declined markedly). The species was stable in north-west Europe during 1990-2000, but declined around the Baltic and in Russia. Although the trend in Iceland was unknown, the species's population has clearly not yet recovered to the level that preceded its decline.
The Canadian Wildlife Service estimates the Dunlin population at 3,934,000 birds worldwide, with 1,325,000 in North America. Of that group, 500,000 birds make up the Pacific Coast population. Dunlin are currently the second most common shorebird in Washington, and the most common of Washington's wintering shorebirds, but numbers have declined in the Northwest in recent decades. There has been little habitat destruction or disturbance on the breeding grounds to date, but the migration and wintering grounds are threatened by destruction of habitat. There is currently no reliable information about population status or trends for Dunlin range-wide, so it is unknown if the trend in the Northwest is due to a decrease in population or a shift in range. Dunlin are considered an indicator species for assessing the health of Holarctic ecosystems, so determining range-wide population trends should be of high priority as reduction in their numbers could indicate that other species that use these ecosystems are at risk.
On the breeding grounds, insects and insect larvae are the most important source of food. In coastal habitats, Dunlin also eat marine worms, small crustaceans, mollusks, and other aquatic creatures. They sometimes eat seeds and leaves.
This species has a large range, with an estimated global Extent of Occurrence of 1,000,000-10,000,000 km². It has a large global population estimated to be 4,200,000-6,400,000 individuals (Wetlands International 2002). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. [conservation status from birdlife.org]
Males typically arrive first on the breeding grounds. Pairs form when females arrive, but if arrival on the breeding grounds is delayed due to weather, pairs may form prior to arrival. Former mates often use the same territory as in the previous year. The male starts a few scrapes, which may be lined with grass, sedge, and willow leaves. The female chooses one and finishes the construction. The nest is usually well hidden under a clump of grass or on a hummock. Both parents incubate the four eggs for 20 to 22 days. The young leave the nest shortly after hatching and find their own food. Both parents tend the young, although the female usually abandons the group within a week of hatching. The male generally stays with the young until they are close to fledging, typically about 19 days.
Migratory. Variety of migration strategies, from short coastal flights to long, non-stop flights overland on broad front. Race arctica moves from Greenland through Iceland, Britain and W France to Morocco and W Africa, primarily to Banc d´Arguin, Mauritania; arrives in Africa from late Jul and departs mainly Mar to early Apr; return migration farther W up W Britain, probably overflying Iceland. Race schinzii passes through Britain, France and Portugal to NW Africa; few may winter in SW England; continental birds move N up continental coasts, when fewer reach Britain than after breeding. Race alpina winters in Europe and NW Africa; easternmost birds migrate farthest; many moult in Wadden Sea or Wash, arriving from Jul, followed by W movements in Oct-Nov to British Is; birds wintering in E Mediterranean make long distance, flights overland across E Europe. At least 3 races move down E Asian coast, where passage recorded through Ussuriland, Korea, Japan, Hong Kong and coastal China. Race articola stages in W Alaska, and crosses Bering Strait to E Asian winter quarters. Almost entire population of pacifica uses Copper R Delta, SE Alaska, as spring staging site. Some 1-year-old birds remain in non-breeding range all year.