Dunlin

The Dunlin is one of the most abundant and widespread sandpipers in the Northern Hemisphere, familiar to birders for its huge, tightly coordinated flocks that wheel and turn in unison over coastal mudflats.

In breeding plumage, Dunlins are unmistakable: a bright rufous back contrasts with a bold black patch on the lower belly, a pattern shared by no other common sandpiper. Nonbreeding birds are much plainer — soft gray-brown above and white below — and are best told by their structure and behavior rather than color.

The bill is moderately long and distinctly drooped at the tip, a useful mark at any season, and the legs are black.

Key field marks

• Black belly patch contrasting with rufous back in breeding plumage — diagnostic
• Plain gray-brown upperparts, white underparts in nonbreeding plumage
• Moderately long, black bill with a distinct downward droop at the tip
• Black legs
• Tends to feed in a slightly hunched posture
• Forms dense, fast-flying flocks that twist and turn together

Similar species

• Curlew Sandpiper: longer, more evenly curved bill, white (not gray) rump, longer legs, and brick-red (not black-bellied) breeding plumage.
• Western Sandpiper: smaller, shorter, straighter bill with only a slight droop, rufous confined to crown and scapulars.
• Purple Sandpiper: darker overall with yellowish leg base, found on rocky rather than muddy shores.

Habitat

Outside the breeding season, Dunlins are classic birds of coastal mudflats, estuaries, and tidal marshes, where they gather in some of the largest flocks of any shorebird.

Range and migration

They breed on Arctic and subarctic tundra across North America, Europe, and Asia. Wintering grounds include temperate coastal areas of North America, Europe, and Asia, where Dunlins often form spectacular, dense flocks numbering in the tens of thousands at major estuaries.

Behavior

Dunlins are highly gregarious outside the breeding season, forming dense flocks that perform dramatic aerial maneuvers, wheeling and flashing alternately dark and light as they turn in unison — a defense against aerial predators like falcons.

Voice

The flight call is a harsh, reedy "kreee" or trilling "jeeep," often heard from flocks in flight.

Feeding

They forage steadily, walking with a slightly hunched posture and rapidly probing soft mud for insects, marine worms, and small mollusks.

Nesting and breeding

Pairs nest on the ground on Arctic or subarctic tundra, often near water; the female typically lays four eggs, and both parents share incubation, though the female often departs before the young fledge.