Red Knots & Semipalmated Sandpipers

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Use our interactive map to learn about the sites most used by Semipalmated Sandpipers and Red Knots during their migration across North America.

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Semipalmated Sandpipers are small, measuring about 13–15 cm, with black, moderately long bill and legs, and a short neck. Their bill may droop slightly at the tip. Their backs are grey-brown and their breasts are usually only lightly marked.1 The slight webbing between their toes that gives Semipalmated Sandpipers their name is only visible at extremely close range.5

Breeding and wintering ranges of the Semipalmated Sandpiper2

Wintering in South America not shown. 2

Story map:


At the end of their Arctic breeding season, some Semipalmated Sandpipers fly up to 4,000 km (2,500 miles) non-stop from southeastern Canada and northeastern United States to their wintering grounds on the northern shores of South America,1 with flocks of up to 300,000 individuals gathering at key stopover and wintering sites.2


The current estimated population of Semipalmated Sandpipers is 2,260,000 individuals.3 While still abundant, a population decline approaching 30% over three generations (22 years) warranted a Near Threatened listing on the IUCN Red List.4 They are also identified in Canada, Mexico and the United States as a species of high conservation concern.


During the summer, Semipalmated Sandpipers breed and nest in the Arctic tundra, usually near water such as beaches and mudflats. During migration, they can be found in coastal and intertidal zones, as well as along inland lake shores and marshes.5 Their mostly coastal overwintering habitat includes beaches, intertidal mudflats, shallow lagoons and saltmarshes.6


Three Semipalmated Sandpiper populations breed in northern Canada and in Alaska in the United States: the western (Alaska) population represents about 64% of the population, while the central (western Canadian Arctic) and eastern (eastern Canadian Arctic) populations together represent nearly 36%.1

During spring (northbound) migration, these populations fly across northeastern North America, including the interior United States and northern Canada, to their Arctic breeding grounds. During fall (southbound) migration, eastern population flocks undertake nonstop trans-oceanic flights up to 4,000 km (2,500 miles), from southeastern Canada and northeastern United States to northern South America.2 Overwintering sites along the Pacific coast stretch from Mexico to Peru, while on the Atlantic coast, sites stretch from the Yucatan and West Indies south to central Argentina, with large flocks congregating along the coast of Suriname and French Guiana.6,7


During the breeding season, Semipalmated Sandpipers mostly eat insects, as well as spiders, snails and seeds.5 Due to partially webbed feet and a specialized bill and tongue, these birds capitalize on the invertebrate-rich mudflat environment. When migrating, they eat a variety of invertebrates to build up the energy reserves required for their long flights—approximately 60% of Semipalmated Sandpipers stop in Delaware Bay4 to eat horseshoe crab eggs on their way to the Arctic.


Cornell Lab of Ornithology. 2017. All About Birds online bird guide. Semipalmated Sandpiers. Online at: <>. Accessed on 25 July 2017.

Cornell Lab of Ornithology. 2017. Birds of North America. Semipalmated Sandpiper. Online at: <>. Accessed on 25 July 2017.

Andres, B.A., P.A. Smith, R.I.G. Morrison, C.L. Gratto-Trevor, S.C. Brown, and C.A. Friis. 2012. Population estimates of North American shorebirds. Wader Study Group Bulletin 119(3): 178–194.

BirdLife International. 2016. Calidris pusilla. The IUCN Red List of Threatened Species 2016. e.T22693373A93400702. Online at: <>. Downloaded on 25 July 2017.

National Audubon Society. 2017. Guide to North American birds. Semipalmated Sandpiper. Online at: <>. Accessed on 25 July 2017.

del Hoyo, J., A. Elliott, and J. Sargatal. 1996. Handbook of the birds of the world, vol. 3: Hoatzin to auks. Barcelona, Spain: Lynx Edicions.

Chandler, R. 2009. Shorebirds of the Northern Hemisphere. London: Christopher Helm.

Semipalmated Sandpiper bird song credit: William W. H. Gunn/Macaulay Library at the Cornell Lab of Ornithology

Photo credit: Brad Winn, Manomet