Western Sandpiper

Calidris mauri

(c) John Cassady
  • SCOLOPACIDAE
  • Snipe, Sandpipers, Phalaropes, and allies
  • Charadriiformes
  • Chichicuilote occidental
  • Bécasseau d'Alaska
Introduction

This species is probably the most numerous shorebird in the Western hemisphere. Despite this, biologists fear that it may be in decline, though exact population trends beg further study. Due to a variety of potential threats, the U.S. Fish and Wildlife Service considers the Western Sandpiper a Species of high concern. The Canadian Wildlife Service classifies it as a species of moderate concern.

Appearance Description
Superficially, Western Sandpiper is very similar to two other species of small, sparrow-sized sandpipers (Least and Semipalmated sandpipers). Inexperienced observers often find this group of birds extremely difficult to identify. In fact, many bird watchers simply refer to all small sandpipers as "peeps", a name derived from the call they make when disturbed. Of the "peeps", Western Sandpiper is usually the easiest to distinguish. At about 6 inches in length, with a 14-inch wingspan, Western Sandpiper is slightly larger than either Least Sandpiper or Semipalmated Sandpiper. It is pale white and gray, overall, with a slightly drooping black bill and long black legs. In spring, its plumage becomes far more intricate, as the feathers on the back and sides attain a rich mix of brown, black and reddish hues. The breast becomes heavily streaked, and the bird develops a rufous wash across either side of the back, as well as on the face and crown. In flight, the underside of the wing is pale at all times of the year, while the top is gray, streaked with white.
Range Map
Courtesy Kenn Kaufman
Range Distribution
The Western Sandpiper breeds almost entirely around the western coast of Alaska. The breeding range begins just north of the Alaska Peninsula, and extends all the way up the western coast to Barrow. A small Siberian population also exists on the eastern edge of the Chukotskiy Peninsula. In winter, the species disperses far and wide. Western Sandpipers can be found as far away as the northeastern coast of South America, and as far north along the Atlantic coast as New Jersey. The largest concentrations of wintering birds occur in Mexico and Central America.
Habitat
In winter, spring, and fall, this species can be found on shorelines, beaches, or within tidal estuaries. While it is generally a coastal bird, it can also be found far inland during migration, usually on mudflats or in flooded fields. In summer, Western Sandpiper inhabits the Alaskan tundra, where it nests in dry, grassy areas near low marshes, ponds or lakes.
Feeding
Western Sandpiper feeds by walking over muddy areas or wading in shallow water, probing the mud constantly in search of prey items. In dry areas, food can also be located visually. Its diet is varied; common prey includes flies, beetles and other insects, as well as worms, small crustaceans, mollusks, and even seeds.
Reproduction
Males arrive on the breeding grounds earlier than the females. Each male establishes a territory, which is advertised to arriving females with the performance of frequent display flights. Prior to the arrival of the females, he excavates several nest scrapes within his territory. Once he has attracted a mate, she chooses the scrape that suits her best, and nesting begins. Materials such as lichen or leaves are added to the nest, and three or four cream colored, streaked eggs are laid. Both parents share incubation duties, and the eggs hatch within about three weeks. Western Sandpiper chicks leave the nest within 24 hours of hatching, and are capable of feeding themselves almost immediately. One or both parents accompany the chicks until they learn to fly, but males are more likely to remain with the chicks than are females. Chicks take flight within three to four weeks, at which point they are deserted by the remaining parent(s). Immature birds form flocks on the breeding grounds, then embark on their first southerly migration together by the end of August.
Migration
During migration, Western Sandpipers tend to move in flocks separated by gender. In spring, males arrive first at the breeding grounds. In fall, females often leave their mate and chicks soon after hatching to form flocks with other females. Males tend to winter further north than females. The northbound migration of Western Sandpipers can be truly fantastic, with hundreds of thousands to millions of birds arriving nearly simultaneously at certain migratory staging areas. The Western Sandpiper makes its way up and down the coast in spring and fall, respectively, via a series of short flights from one stopover point to the next. The route seems to be specifically timed; banded adults have been recovered arriving at a Central American site on exactly the same date from year to year. While the migratory route is generally coastal, the species is also known to migrate over land, specifically between the southern Atlantic and Gulf coasts of North America and the Pacific Northwest.
  • 3,500,000
  • 3,500,000
Population Status Trends
Despite, or perhaps due to, the fact that Western Sandpipers are so abundant, population estimates and trend assessments have proven difficult to ascertain. This species is thought to be decreasing, but estimates are based largely upon data gathered from a scant few migratory staging points, and may not be representative of the overall picture. Maximum seasonal counts from several major migratory stopover points between California and British Columbia have declined over the past few decades, leading researchers to fear that the species, while still extremely numerous, may in fact be in trouble.
Conservation Issues
The Western Sandpiper is abundant and remarkably well studied, yet there is no solid conservation strategy in place for the species. It is particularly vulnerable to habitat loss, especially at the major migratory stop over areas where millions of these birds are concentrated each spring. Coastal development and loss of habitat to increased agricultural activity are two major concerns. Western Sandpipers rely heavily upon a handful of migratory stopover points. Alaska's Cooper River Delta is a prime example; up to two million Western Sandpipers have been counted here in a single day at the height of spring migration! An environmental disaster such as an oil spill at any one of the species' major migratory staging areas could prove fatal to hundreds of thousands of birds at once. Accurate monitoring of Western Sandpiper numbers at concentration points along its migratory route will be a crucial step toward determining whether its numbers are truly decreasing, as is currently presumed.
What You Can Do
Find out about actions you can take including Audubon programs and activities.
More Information
Learn more about this species and other birds through these resources.
Natural History References
Fernández, G., N. Warnock, D. L. Lank, and J. B. Buchanan. 2006. Conservation Plan for the Western Sandpiper, version 1.0. Manomet Center for Conservation Science, Manomet, Massachusetts.

Kaufman, Kenn. 1996. Lives of North American Birds. Houghton Mifflin Company, New York.

Richards, Alan. 1988. Shorebirds - A Complete Guide to Their Behavior and Migration. Gallery Books. New York.

Wilson, W. H. 1994. Western Sandpiper (Calidris mauri). In The Birds of North America, No. 90 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.
Conservation Status References
Wilson, W. H. 1994. Western Sandpiper (Calidris mauri). In The Birds of North America, No. 90 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.

Fernández, G., N. Warnock, D. L. Lank, and J. B. Buchanan. 2006. Conservation Plan for the Western Sandpiper, version 1.0. Manomet Center for Conservation Science, Manomet, Massachusetts.

Richards, Alan. 1988. Shorebirds - A Complete Guide to Their Behavior and Migration. Gallery Books. New York.