Western Sandpiper - Field Marks

The massing of Western Sandpipers at Grays Harbor, Washington, is truly an impressive sight. In late April, as many as one-half million individuals have been seen there in one day, and seeing several hundred thousand is not uncommon.

Western Sandpiper
Calidris mauri

Similar to the Semipalmated Sandpiper but a little larger, more colorful in breeding plumage, and more western in its distribution. Western Sandpipers nest mostly in Alaska and migrate mostly along the Pacific Coast, but many reach the Atlantic Coast in fall and remain through the winter. Of the various dull gray sandpipers to be found commonly on coastal beaches in winter, Western is the smallest. This and the other very small sandpipers are known collectively as "peeps."

Field Marks
This and the Least Sandpiper are the two common small "peeps" in most of the West (west of the Plains). The Western is the larger bird; its bill is very noticeably longer (especially in females), thicker at the base, and droops slightly at the tip. Legs black. Breeding adults are heavily streaked on the breast. They show rusty on the scapulars and have a rusty crown and ear patch. (A trace of rusty may persist on the scapulars in fall, giving a two-toned effect.) In winter, gray or gray-brown; perhaps the palest "peep."

6-7" (15-18 cm)

Similar Species
Very similar to Semipalmated Sandpiper; but may be a trifle larger. In typical adult females the bill is definitely thicker at the base and longer, drooping slightly at the tip. Summer adults are rustier on the back and crown. Because of their shorter bills, many males in fall or winter plumage are almost impossible to separate from Semipalmateds except by voice. The latter species seldom winters in the United States, but the Western does. If the birds do not call, it is fairly safe to assume they are Westerns.

A thin jeet or cheep; not as drawn out as note of Least and unlike the soft chit of Semipalmated.

Breeds in Alaska. Winters from southern United States to Peru.

Western Sandpiper - Range Map

From breeding grounds in Alaska and eastern Siberia, migrates southeast to wintering areas on both coasts of North and South America. Apparently migrates in series of short to moderate flights, without long overwater flights of some shorebirds.

Shores, beaches, mudflats; in summer, dry tundra. Migrants and wintering birds are typically on open shorelines, mudflats, sandy beaches, tidal estuaries. In winter mostly along coast, few remaining inland then. Breeds on tundra slopes, choosing dry sites with low shrub layer and with marshes nearby for feeding.

Diet: Includes insects, crustaceans, mollusks, marine worms. On breeding grounds, eats mostly flies and beetles, also other insects, spiders, small crustaceans. Diet during migration and in winter varies. On coast eats many amphipods and other crustaceans, small mollusks, marine worms, insects. Inland migrants probably eat mostly insects.

Behavior: Forages by walking in shallow water or on mud and probing in mud with bill; also feeds by searching visually and picking up items from surface of shore.

Male sings while performing display flight over territory. On ground, unmated male approaches female in hunched posture, tail raised over back; repeatedly gives trilled call.

Nest: Site is on ground, usually under low shrub or grass clump. Nest is shallow depression with sparse lining of sedges, leaves, lichens. Male makes several nest scrapes, female chooses one.

Eggs: 4, sometimes 3, perhaps rarely 5. Whitish to brown, with darker brown spots. Incubation is by both parents, about 21 days. At first, female incubates most of time, male only during midday, but male's proportion increases later. Female sometimes departs before eggs hatch.

Young: Downy young leave nest soon after hatching. Sometimes both parents care for the chicks, but often the female deserts after a few days, leaving the male to care for them. Young feed themselves. Age at first flight about 17-21 days.

Still abundant, but vulnerable because high percentage of population may stop during migration at a few key points, such as Copper River Delta in Alaska. Declining numbers noted in some areas.

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