Dunlin (Calidris alpina)

[order] CHARADRIIFORMES | [family] Scolopacidae | [latin] Calidris alpina | [UK] Dunlin | [FR] Becasseau variable | [DE] Alpen-Strandlaufer | [ES] Correlimos Comun | [NL] Bonte Strandloper

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.

North America, Eurasia : North

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.

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.

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 an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

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 dArguin, 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.