Dunlin

Calidris alpina

(c) Howard B. Eskin
  • SCOLOPACIDAE
  • Snipe, Sandpipers, Phalaropes, and allies
  • Charadriiformes
  • Correlimos común
  • Bécasseau variable
Introduction
Widespread and locally common in many parts of the northern hemisphere, the Dunlin has been the object of many studies, and has dazzled many observers with its large flocks and swift, synchronized flights. On pointed, falcon-like wings, this medium-sized sandpiper can reach speeds of 110 miles per hour. For most the year, the Dunlin's plumage is a drab grayish-brown, or dun color, that inspired the bird's common name over 450 years ago.
Appearance Description
Dunlin weigh about 2.1 ounces, grow to 8.5 inches, and have a 17-inch wingspan. The remarkable contrast between the Dunlin’s winter and summer plumage is reflected in its French common name, “Variable Sandpiper.” Dunlin sport a red back and black belly, separated by white in the flanks, during the breeding season; an old name for this species was “Red-backed Sandpiper.” The bird’s head and chest are grayish. The Dunlin’s relatively long, black bill droops toward the tip. Black legs distinguish it from most other medium-sized sandpipers. In winter, the plain grayish brown of the upper parts and the dirty white of the under parts help this species blend in with its sandy, muddy habitat.
Range Map
Courtesy Kenn Kaufman
Range Distribution
Several subspecies of Dunlin breed in North America. Western populations breed coastally from western Alaska north through the Arctic National Wildlife Refuge to Canada’s Northwest Territories. Eastern populations breed from the peninsulas of Canada’s Nunavut Territory, southward along the western shores of Hudson Bay. Along the Pacific coast, Dunlin winter from Alaska to the state of Nayarit, Mexico, and along the Atlantic and Gulf coasts from Massachusetts to Northern Veracruz, Mexico.
 
A legend for the range map to the right can be found here.
Habitat
During the breeding season, Dunlin inhabit a variety of landscapes: tundra, shallow marshes, melt water edges, wet meadows, and mud flats. Wintering and migrating Dunlin frequent shorelines and estuaries. Inland meadows, farmland, and conservation lands provide vital alternative habitats, particularly when coastal habitats are unproductive.
Feeding
Outside the breeding season, Dunlin probe in sand or mud for marine worms like the pile worm, crustaceans like beach hoppers, and mollusks like the Baltic macoma clam. Migrating Dunlin often feed at night. On the breeding grounds, this shorebird forages by sight, capturing larval midges, adult flies, and beetles.
Reproduction
Throughout May, male Dunlin arrive on their breeding grounds and usually establish territories in advance of their mates’ arrival. Pairs often re-form in successive years and are monogamous for the season. Males perform aerial displays to maintain pair bonds and create one or more scrapes for the female to inspect. The cup is first compacted with the feet, then widened with the breast, and lined with a loose collection of leaves and grasses.
 

Females lay four buff, blue-green, or olive eggs, splotched and scrawled with warm browns. Both sexes incubate the eggs for about three weeks, at which time the chicks emerge, ready to walk, preen, forage, and hide. Within a few days, they can keep themselves warm. Females tend the brood for about six days, but males usually remain until the young can fly. Juvenile Dunlin form flocks and move to interior locations before joining adults on coastal staging areas prior to fall migration.

Migration
Dunlin migrate in large, sometimes enormous, flocks that baffle predators with rapid, synchronized maneuvers. The Dunlin’s short to medium-range migration begins in March and follows traditional routes along both coasts and interior flyways, depending on the subspecies. North American Dunlin molt in September before migrating south from staging areas near their breeding grounds. As a result, Dunlin are one of the last shorebirds to arrive on the shores of the United States in the late fall.
CBC Graph
Graph Legend
Annual Population Indices
  • 5,300,000
  • 1,525,000
  • declining population; moderate conservation concern
Population Status Trends
In North America, Dunlin populations are large and apparently stable, with a few exceptions. Christmas Bird Count data from the mid-1980s to the early 1990s indicates a decline in Dunlin wintering on the Pacific coast, as well as a decline in the Arctic subspecies on its breeding territory.
 
An explanation of the Annual Indices graph displayed to the right can be found here.
Conservation Issues
Widespread and common for so long, the presence of Dunlin indicates the health of wetland habitats and thereby helps direct conservation efforts. This sandpiper depends on farmland near traditional wintering sites. Rainy and cold weather conditions motivate Dunlin to seek alternative foraging and roosting locations. Good management of lands adjacent to traditional coastal preserves helps insure the continued abundance of species like the Dunlin.
 

Dunlin also illustrate the importance of protecting areas outside migratory stopover locations. The Copper River Delta, just outside Cordova, Alaska, hosts millions of shorebirds in the spring. This delta is largely protected by Alaska as both a “shorebird reserve unit” and a “critical habitat area.” As Dunlin arrive in Alaska, they stage just outside the protected lands, along Controller Bay. An estimated 25% of all shorebird migrants first set down along this bay. The Dunlin’s migration habits highlight the need for a comprehensive management plan for protecting flyways, rather than a few key reserves.

What You Can Do
Look for Dunlin on beaches, wet fields, and mudflats from October through May. Join a local bird walk to spot this sometimes snazzy sandpiper.
 
Witness great flocks of Dunlin at the Copper River Shorebird Festival in Cordova, Alaska, scheduled for May 3 to 6, 2007. Attend workshops on bird watching and field trips to see some of the estimated five million shorebirds that use the Copper River during spring migration.
 
Pets, children, and walkers can disturb shorebirds by approaching too closely. Respect Dunlin and give them room to forage and rest along coastal shorelines.
 
For more actions you can take, including Audubon activities, please visit our resources page.
More Information
Visit our resources page for more information about this species.
Natural History References
Kaufman, Kenn. Lives of North American Birds. Houghton Mifflin Company, New York, 1996.
 
Luis, A. and Goss-Custard, J. “Spatial organization of the Dunlin Calidris alpina L. during winter - the existence of functional units.” Bird Study 52:2 (July 2005) 97-103.
 
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, New York, 2000.
 
Warnock, N. D., and R. E Gill. 1996. Dunlin (Calidris alpina). In The Birds of North America, No. 203 (A. Poole and F. Gill, Eds.). The Academy of Natural Sciences, Philadelphia, and the American Ornithologists’ Union, Washington, D.C.
Conservation Status References
Donaldson, G. M., et al. Canadian Shorebird Conservation Plan. Canadian Wildlife Service. Minister of Public Works and Government Services, Ottawa, Ontario (2000).
 
Evans Ogden, L. J., K. A. Hobson, D. B. Lank, and S. Bittman. 2005. “Stable isotope analysis reveals that agricultural habitat provides an important dietary component for nonbreeding Dunlin.” Avian Conservation and Ecology - Écologie et conservation des oiseaux 1(1:): 3.
 
Kaufman, Kenn. Lives of North American Birds. Houghton Mifflin Company, New York, 1996.
 
Shepherd, Phillipa C. F., Lesley J. Evans Ogden, and David B. Lank. “Integrating marine and terrestrial habitats in shorebird conservation planning.” Wader Study Group Bulletin 100 (April 2003) 40-42.
 
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, New York, 2000.
 

 

U. S. Shorebird Conservation Plan. 2004. High Priority Shorebirds – 2004. Unpublished Report, U.S. Fish and Wildlife Service, 4401 N. Fairfax Drive, MBSP 4107, Arlington, VA 22203 (5 pages).
 

Warnock, N. D., and R. E Gill. 1996. Dunlin (Calidris alpina). In The Birds of North America, No. 203 (A. Poole and F. Gill, Eds.). The Academy of Natural Sciences, Philadelphia, and the American Ornithologists’ Union, Washington, D.C.