Semipalmated Sandpiper

The Semipalmated Sandpiper is one of the most numerous shorebirds in North America, named for the small amount of webbing between its toes ("semipalmated" meaning partly webbed), a feature shared with a few other sandpipers.

It is compact and rather plain, with grayish-brown upperparts showing only limited rufous tones even in breeding plumage, distinguishing it from the brighter Western Sandpiper. The bill is short, straight, and stubby — notably shorter than the fine, drooped bill of the Western Sandpiper — and the legs are black.

During migration, this species forms some of the largest shorebird concentrations on the planet, with hundreds of thousands gathering at key stopover sites.

Key field marks

• Short, straight, blunt-tipped bill
• Grayish-brown upperparts with limited rufous tones, even in breeding plumage
• Black legs
• Partial webbing between toes (semipalmated), visible only at close range
• Compact, small "peep" build

Similar species

• Western Sandpiper: longer, finer bill with a distinct droop, brighter rufous tones in breeding plumage.
• Least Sandpiper: smaller with yellowish-green legs rather than black.
• Bill length and shape are the most useful ways to separate Semipalmated from Western Sandpiper in mixed flocks.

Habitat

Semipalmated Sandpipers are classic mudflat and estuary birds, gathering in dense flocks on open tidal flats during migration and winter.

Range and migration

They breed on Arctic tundra across northern Canada and Alaska. One of their most famous migratory stopovers is the Bay of Fundy in eastern Canada, where enormous flocks gather to feed before making long nonstop flights to wintering grounds, which are concentrated mainly along the coasts of South America.

Behavior

This species is highly gregarious, forming some of the densest shorebird flocks in the world at key staging areas, where birds feed intensively to build fat reserves for long overwater migratory flights.

Voice

The flight call is a short, low "chrup" or "chit," distinct from the higher, thinner calls of the Western and Least Sandpipers.

Feeding

They probe and peck rapidly in soft mud for small invertebrates, including insects and marine worms, often feeding shoulder-to-shoulder with hundreds or thousands of other individuals.

Nesting and breeding

Pairs nest on the ground on open Arctic tundra, often near water; the female lays four eggs in a shallow scrape, and both parents share incubation before the young quickly become independent and mobile.