Dunlin

About

The Dunlin is a small, migratory shorebird belonging to the sandpiper family. It is characterized by its slightly downcurved bill and, in breeding plumage, a distinctive black belly patch. It is one of the most widespread and numerous shorebirds, found across Arctic and subarctic regions, migrating to temperate and tropical coasts for winter.

Size & lifespan

Length

16-22 cm (6.3-8.7 in)

Wingspan

32-39 cm (12.6-15.4 in)

Weight

30-80 g (1.1-2.8 oz)

Lifespan

Up to 10-12 years in the wild

Diet

Carnivore (primarily invertebrates)

Physical characteristics

Plumage

Breeding plumage features a rufous back with black streaking, a white belly with a prominent black patch, and a white supercilium. Non-breeding plumage is duller, grayish-brown above, white below, with faint streaking on the breast. Juveniles resemble non-breeding adults but have more distinct streaking on the flanks and breast, and often a reddish wash on the back.

Beak shape

Medium-length, slender, and slightly downcurved black bill.

Eye color

Dark brown

Leg color

Black

Distinguishing features

The slightly downcurved bill is a key feature in all plumages. The black belly patch in breeding adults is diagnostic. In non-breeding plumage, its overall grayish tone and bill shape help distinguish it from other small sandpipers.

Juvenile appearance

Juveniles have a scaly-patterned rufous-brown back, a buffy wash on the breast with fine streaking, and often a faint blackish belly patch that is less defined than in adults. Their upperparts are often brighter and more patterned than non-breeding adults.

Seasonal changes

Dramatic change between breeding and non-breeding plumages. Breeding plumage (late spring to late summer) is characterized by the rufous back and black belly patch. Non-breeding plumage (late summer to early spring) is a drabber gray-brown above and white below, lacking the distinctive black belly.

Sexual dimorphism

Males and females are generally similar in plumage, though females tend to be slightly larger and have a slightly longer bill on average. The black belly patch in breeding plumage can be slightly larger in females.

How to identify

1. 1

   Bill Shape

   Look for the medium-length, slender bill that is distinctly, though subtly, downcurved at the tip. This is a consistent feature across all ages and plumages.

2. 2

   Black Belly Patch (Breeding Plumage)

   In late spring and summer, the prominent black patch on the lower belly is unmistakable and diagnostic for adult Dunlins.

3. 3

   Plumage Coloration

   Breeding adults have a rich rufous back with black streaking. Non-breeding adults are uniformly grayish-brown above and white below, with faint streaking on the breast. Juveniles have a scaly back and often a buffy breast.

4. 4

   Leg Color

   Always black legs and feet.

5. 5

   Behavior

   Observe their feeding behavior – they often probe deeply into mud. Also, note their tendency to form large, cohesive flocks, especially during migration and winter.

6. 6

   Call

   Listen for the distinctive, reedy, slightly descending 'kreep' call, often given in flight.

Habitat & range

Biomes

Tundra, coastal wetlands, estuaries, mudflats, sandy beaches, salt marshes, freshwater marshes, agricultural fields (during migration).

Geographic range

Breeds in Arctic and subarctic regions of Eurasia and North America. Winters along temperate and tropical coasts of Europe, Africa, Asia, and North America.

Elevation range

Primarily found at sea level, but can occur at higher elevations in tundra breeding grounds.

Preferred environments

During breeding, prefers wet tundra with sedges and mosses. During migration and winter, favors intertidal mudflats, sandy beaches, and shallow coastal waters rich in invertebrate prey.

Behavior

Activity time

Diurnal, but also forages at night during low tide, especially on moonlit nights.

Feeding habits

Forages by probing its bill into soft substrates (mud, sand) to extract invertebrates. Also picks prey from the surface. Often feeds in large, dense flocks, moving synchronously across mudflats. Diet includes marine worms, small crustaceans, mollusks, and insect larvae.

Social behavior

Highly social, especially outside the breeding season. Forms large, sometimes immense, flocks on migration and in wintering areas. These flocks can number in the tens of thousands. On breeding grounds, they are more territorial and solitary or in loose colonies.

Flight pattern

Flight is strong and direct, often in tightly packed, highly coordinated flocks during migration and winter. When flushed, they perform rapid, erratic maneuvers. On breeding grounds, display flights involve circling and hovering.

Migration pattern

Long-distance migrant. Breeds in the Arctic and subarctic and migrates south to temperate and tropical coastal areas. North American breeders winter along the Atlantic and Pacific coasts of North America, and occasionally further south. Eurasian breeders winter along coasts of Europe, Africa, and Asia.

Territoriality

During the breeding season, males establish and defend territories, often with aerial displays and vocalizations. Outside of breeding, they are not territorial and feed communally.

Breeding & reproduction

Breeding season

Late May to August, peaking in June-July.

Nesting habits

Nests are shallow scrapes on the ground, typically in wet tundra, lined with leaves, moss, and lichens. Often concealed within dense vegetation.

Clutch size

Usually 4 eggs.

Egg description

Typically 4 eggs, pear-shaped, olive to buffy-brown with dark brown spots and blotches, concentrated at the larger end.

Incubation period

20-22 days, shared by both parents.

Fledging period

Chicks are precocial and leave the nest shortly after hatching. They are capable of flight at about 19-21 days old.

Parental care

Both parents incubate and care for the young. Females often depart before the young fledge, leaving the male to complete parental duties.

Where to find

Field tips

1. Scan large flocks. Dunlins often occur in large, mixed flocks with other shorebirds. Carefully scan these groups for the distinctive bill shape and, in breeding season, the black belly.
2. Observe feeding behavior. Watch how they probe the mud. Their slightly downcurved bill is well-suited for this, and their methodical foraging can be a good identification clue.
3. Check tides. Shorebirds are most active and visible during falling and low tides when mudflats are exposed. Plan your visits accordingly.
4. Use a scope. For distant flocks on large mudflats, a spotting scope is invaluable for picking out individual features like bill shape and plumage details.
5. Listen for calls. Their 'kreep' call is quite distinctive and can help locate them, especially in flight or when obscured by vegetation.

Similar species

Quick facts

Global Population:

Estimated 4.9-6.7 million individuals

Migration Distance:

Can migrate thousands of kilometers between breeding and wintering grounds.

Subspecies:

Recognized 10 subspecies (e.g., C. a. alpina, C. a. arctica, C. a. pacifica, C. a. hudsonia), varying slightly in size, bill length, and plumage tones.

Ecological Role:

Important consumer of intertidal invertebrates and a prey item for raptors and gulls.

Fun facts

• Dunlins are known for their spectacular synchronized flight displays in large flocks, often called 'murmurations,' which can be breathtaking to witness.
• The name 'Dunlin' is thought to derive from 'dun,' meaning dull brown, referring to its non-breeding plumage.
• Some Dunlins undertake one of the longest migrations of any shorebird, traveling from the high Arctic to tropical latitudes.
• The length and curvature of the Dunlin's bill can vary significantly between subspecies, which helps them exploit different food resources in their respective ranges.

Scientific classification

Kingdom

Animalia

Phylum

Chordata

Class

Aves

Order

Charadriiformes

Family

Scolopacidae

Genus

Calidris

Species

Calidris alpina

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