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Photo by Larry Master
Photo Copyright Larry Master
Dunlin
Calidris alpina
NatureServe conservation status
Global (G-rank): G5
State (S-rank): SNA
External links
General information
The dunlin, Calidris alpina, is a rare transient in Utah. Flocks are occasionally seen in the state in wetlands during migration between breeding grounds on Arctic coasts and wintering grounds along the Pacific and Atlantic coasts of North America and northern South America.
Nesting areas are generally in coastal tundra grasslands. Usually four eggs are laid during June in a cup-shaped hollow that is lined with grasses and leaves. Incubation duties are shared by both sexes in most cases, but sometimes the male alone may incubate the eggs. Eggs hatch after 21 or 22 days, and young leave the nest almost immediately. The young feed themselves, but are guarded by both parents until they are able to fly after about 25 days. In some cases, the male's role may become more important as the young grow, and the female may leave before the young are independent. This shorebird feeds on a variety of invertebrates, including bivalves, amphipods, annelids, and insect larvae.
Phenology
Spring migrants in south-central Alaska rested during high tides and fed most heavily during falling tides (Senner et al. 1989). On the Yukon-Kuskokwim Delta, Alaska, roosting varied with time of day, tide level, and season (Handel and Gill 1992).
Species range
BREEDS: northern Alaska, northern Mackenzie, northeastern Keewatin, and southern Somerset Island south to coastal western Alaska, Southampton Island, northeastern Manitoba, and northern Ontario; eastern Greenland, Iceland, Sptizbergen, Novaya Zemlya, arctic coast of Siberia, Kamchatka Peninsula, and Sakhalin Island south to British Isles, Baltic region, northern Russia, and northern China (AOU 1983, Browning 1991). WINTERS: along Pacific coast from southeastern Alaska south to Baja California and Sonora, on Atlantic-Gulf-Caribbean coast from Massachusetts south to Florida, west to Texas, south to Yucatan Peninsula; in Old World from southern Europe and southern Asia to Cape Verde Islands, northern Afria, Arabia, Indian coast, and Formosa (AOU 1983); occasionally in Hawaii. Nonbreeders often summer in winter range. The Yukon-Kuskokwim Delta, Alaska, is an important migration stop in western North America (Handel and Gill 1992). See Browning (1991) for information on the distribution of subspecies in northern Alaska and eastern Siberia.
Migration
Migrates mainly along coasts, smaller numbers in interior North America. Begins migrating northward along Atlantic and Pacific coasts of North America in March-April, arrives in northern Alaska in late May. After fledging, juveniles move to coastal habitat in late July and early August in northern Alaska; adults move to upland areas. Departs breeding grounds late August or September. Breeders banded at Point Barrow, Alaska, were recaptured in October at Cape Lazarev, Siberia, and Sakhalin Island (see Browning 1991). Postbreeders roost in large flocks and feed on expansive intertidal mudflats of the Yukon-Kuskokwim Delta, Alaska, from July until early October, then to southeastern Asia and California (Handel and Gill 1992). Southbound migrants reach central California coast by mid-October. Often migrates in large flocks.
Habitat
Nonbreeding: mudflats, estuaries, marshes, flooded fields, sandy or gravelly beaches, and shores of lakes, ponds, and sloughs (AOU 1983, Smith and Connors 1993). In central California, movements from coastal habitats to inland habitats occurred in conjunction with winter storms (heavy rain) (Warnock et al. 1995). On the Yukon-Kuskokwim Delta, Alaska, major diurnal roost sites were adjacent to intertidal feeding areas, provided a unobstructed view of predators, and were close to shallow waters used for bathing (Handel and Gill 1992). Nests in wet coastal tundra (AOU 1983), grass or sedge tundra with pools and bogs. Nests on the ground, usually in drier sites such as strangmoor ridges.
Food habits
During the breeding season feeds primarily on larvae of flies and mosquitoes. During the rest of the year feeds on crustaceans, marine worms, mollusks, and insects. Migrants in spring in south-central Alaska relied heavly on clams, MACOMA BALTHICA (Senner et al. 1989). Consumes large numbers of horseshoe crab eggs in spring at Delaware Bay (Castro and Myers 1993). Runs around feeding areas probing mud and sand with bill.
Ecology
Nonbreeding: often in large flocks, which in some roosting areas may include 10,000s (Handel and Gill 1992). Often seen in association with sanderlings and other shorebirds.
Reproductive characteristics
Breeding begins late May to early June in the Western Hemisphere (clutches completed mainly mid-June in Beaufort Sea area). Both sexes, in turn, incubate 4 eggs for 21-22 days. Nestlings are precocial and downy. Young are independent in about 25 days (Harrison 1978). Often nests near other pairs of dunlins. In northern Alaska, up to 15 nests per sq km have been recorded in several areas of coastal tundra and sites a few miles inland.
Threats or limiting factors
Climate change may affect this species at its typical breeding localities at northern latitudes. Loss of habitat at wintering grounds may also be severe, with some findings as high as 30 - 91% reduction (Warnock and gill, 1996).
References
- Warnock, N. D., and R. E. Gill. 1996. Dunlin (Calidris alpina). Birds of North America 203: 24 pp.
- Baicich, P. J., and C. J. O. Harrison. 1997. A guide to the nests, eggs, and nestlings of North American Birds, Second Ed. Academic Press, San Diego. 347 pp.
