Western Sandpiper

The Western Sandpiper is one of the most numerous small shorebirds in North America, part of the group known informally as "peeps" for their diminutive size and superficial similarity to one another.

In breeding plumage, it shows rufous tones on the crown and scapulars, with dark chevron-shaped markings along the flanks. Nonbreeding birds are plain gray-brown above and white below, much like other peeps. The bill is a key identification feature — noticeably longer and finer than that of the very similar Semipalmated Sandpiper, with a slight downward droop near the tip.

Western Sandpipers migrate in enormous numbers, with key staging areas hosting hundreds of thousands of birds at a time.

Key field marks

• Longer, thinner bill with a slight downward droop, longer on average than Semipalmated Sandpiper
• Rufous tones on crown and scapulars in breeding plumage
• Dark chevron markings along the flanks in breeding plumage
• Black legs
• Small, compact "peep" size

Similar species

• Semipalmated Sandpiper: shorter, straighter, stubbier bill, less rufous overall, and only partial toe webbing shared by both species (not a distinguishing feature in the field).
• Least Sandpiper: smaller, browner, with yellowish-green (not black) legs.
• Dunlin: notably larger with a longer, more strongly drooped bill.

Habitat

Western Sandpipers favor open coastal mudflats, estuaries, and tidal flats, where they feed in dense, mixed flocks with other small shorebirds.

Range and migration

They breed on tundra in western Alaska and easternmost Siberia. During migration, enormous concentrations gather at key stopover sites such as the Copper River Delta in Alaska and the Fraser River estuary in British Columbia, before continuing on to wintering grounds along Pacific, Gulf, and Atlantic coasts from the southern United States to South America.

Behavior

Western Sandpipers are highly gregarious, forming some of the largest shorebird flocks in North America during migration, often mixing with Semipalmated and Least Sandpipers and other small waders.

Voice

The flight call is a thin, high-pitched "jeet" or "cheet," typical of the peep group but slightly more strident than that of the Semipalmated Sandpiper.

Feeding

They probe rapidly in soft mud for small invertebrates, including insects and marine worms, often wading in shallow water at the tide's edge.

Nesting and breeding

Pairs nest on the ground on Arctic tundra, in a shallow scrape lined with lichen and leaves; the female typically lays four eggs, and both parents assist with incubation before the female often departs early, leaving the male to tend the young.