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New Jersey Endangered and Threatened Species Field Guide


Image of Dunlin.Zoom+ Dunlin. © Jan van de Kam

Dunlin

Calidris alpina

Species Group: Bird

Conservation Status

State: Other Classification

 


IDENTIFICATION

Once known as the red-backed sandpiper, the dunlin is among the most well-studied of all sandpipers. A smaller sandpiper at about 8 inches in length, dunlin can be distinguished from some similarly-sized sandpipers by its black legs and a relatively long black bill that droops at the tip. In summer, the face and upperparts are whitish with an unmistakable black patch on belly; the back and head are reddish-brown. In winter, dunlin are considerably more plain, with a white belly, a gray-brown head, neck and breast, and gray wings and back. Juveniles in their first fall have a buff breast and head with a reddish-brown back; lines of dark spots extend from lower breast onto belly and flanks. This plumage is rarely seen outside the dunlin’s breeding grounds in the Arctic, as the juveniles molt into winter plumage on their breeding ground before migrating south.

Image of Range of the dunlin in New Jersey.Zoom+ Range of the dunlin in New Jersey.

DISTRIBUTION AND HABITAT

Like many other New Jersey shorebirds, dunlin are migrants, breeding in the northern Arctic. In North America, their breeding range stretches from southwestern Alaska and the Aleutians north and east to James Bay. Unlike their more particular cousin, the red knot, dunlin inhabit a variety of habitats on their breeding grounds, including tundra, wetlands, melt water edges, wet meadows, shallow marshes, and mudflats.

In winter, the Atlantic population of dunlin ranges from Massachusetts in the north to Northern Veracruz, Mexico in the south. While migrating and wintering, dunlin tend to prefer beaches and coastal mudflats, but they are adaptable here as well. If these coastal habitats are unproductive, they will utilize alternative habitats inland such as farmland, meadows or other conservation lands. Additionally, substantial numbers of dunlin will regularly winter inland along the Gulf of Mexico, the central valley of California, and other areas.

DIET

Dunlin forage mainly by sight on their breeding grounds, capturing insect prey such as larval midges, beetles, and other larval and adult flies. Outside the breeding season, they forage mainly by touch, probing the sand or mud with their long bills for marine worms, crustaceans, and mollusks.

LIFE CYCLE

Male dunlin arrive on the breeding grounds throughout May and begin to establish territories prior to the arrival of the females. Once a mate has been found, dunlin are monogamous during the season, and they will often re-form pairs in subsequent years on the same territory.

Nests are constructed on small hummocks on the ground and are little more than a compacted scrape lined with grass and other vegetation. The female lays four spotted green to olive-buff eggs, and both sexes incubate for about three weeks. The chicks are able to walk within hours and regulate their own body temperature within days. Females tend the brood for about a week, while the male will remain with the chicks until they fledge at about three weeks of age. Juvenile dunlin often form flocks of their own at interior locations before joining the adults at coastal staging areas prior to fall migration. During this time, both juvenile and adult dunlin molt into their winter plumage before heading south. For this reason, they are usually one of the last shorebirds to arrive at southern beaches in the fall.

CURRENT THREATS, STATUS, AND CONSERVATION

Due to their wide geographic distribution and stable numbers overall, dunlin are not considered threatened by any major conservation authority. However, some populations (notably the Pacific subspecies) are in decline. It is suspected that habitat loss due to contamination and continued coastal development may be a factor in this drop. Similarly, global climate change could have as-yet unseen effects on dunlin, whose far-northern breeding territories make them especially vulnerable.

Additionally, dunlin frequently stage in and utilize areas adjacent to protected shorebird reserves. This highlights the need for the protection of migratory flyways and not just isolated pockets of protected habitat.


Text written by Matthew Danihel in 2013.



REFERENCES

  • "Dunlin". National Audubon Society. Accessed: July 30, 2013. Available at: http://birds.audubon.org/species/dunlin.
  • Stokes, Donald, and Lillian Stokes. Field Guide to Birds: Eastern Region. New York, NY: Little, Brown and Company, 1996.
  • Warnock, Nils D., and Robert E. Gill. "Dunlin (Calidris alpina)". Ithaca, NY, 1996. The Birds of North America Online (A. Poole, Ed.).Cornell Lab of Ornithology. Accessed: July 30, 2013. Available at: http://bna.birds.cornell.edu/bna/species/203.

Scientific Classification

Kingdom: Animalia
    Phylum: Chordata
       Class: Aves
          Order: Charadriiformes
             Family: Scolopacidae
                Genus: Calidris
                   Species: C. alpina

Find Related Info: Shorebirds

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