Dunlin  (Calidris alpina)

The dunlin is classified as Least Concern (LC) on the IUCN Red List (1).

The dunlin (Calidris alpina) is one of the hardiest of all shorebirds, breeding far north in the Arctic region and migrating southwards before the onset of winter (3). This species is also renowned for its beautiful breeding plumage, which is distinguished by the reddish cap, bright reddish-brown back and black belly patch, which extends behind its black legs. The head and breast are pale brown. Outside of the breeding season, the dunlin is light brownish-grey with a brownish back, white underparts and a brownish band streaking across the upper breast (2) (4).

The dunlin has a very wide distribution, occurring across nearly all Arctic regions. Its breeding range stretches from east Greenland, across the Russian Arctic to the Alaskan coast of the Bering Sea. There is also an isolated population that breeds in the east Canadian Arctic (5) (6) (7). 

A migratory species, the dunlin has a number of sub-populations that each has differing migration behaviours. For instance, the sub-population that breeds in north-east Greenland migrates through Iceland, Britain and western France to arrive in its west African wintering grounds from late July, returning again between March and early April (5).

During the breeding season, the dunlin is found on moist, boggy ground with tussock tundra, as well as wet coastal grasslands, salt marshes and wet upland moorland. Outside of the breeding season, this species prefers mudflats, but occurs on a wide variety of fresh and brackish habitats, including lagoons, muddy shores, tidal rivers, flooded fields, sandy coasts, lakes and dams (5).

The male dunlin arrives at the breeding grounds first, and pairs are established upon the females’ arrival (4). The males attract a partner by performing display flights, which consist of short glides with stiff arched wings, interrupted by rapid, shallow flutters (2). The male makes a few scrapes on the ground, which are then lined with grass, sedges and leaves. The female chooses one of the scrapes as the nest and finishes its construction (4). The nest is often concealed in vegetation and sometimes in a tuft or tussock (5). Usually 4 eggs are laid, which are then incubated for 20 to 22 days. The young leave the nest shortly after hatching, but are tended by the adults until they are ready to fledge, usually at about 19 days (4). 

Outside of the breeding season, the dunlin is highly gregarious, travelling in groups of up to 1,500 while migrating and residing in groups numbering hundreds of thousands at the wintering grounds. This species is active both during the day and at night (5). It feeds by probing and jabbing with its long bill in the substrate (2). At the breeding grounds, insects and insect larvae are the most important source of food, but elsewhere its diet is more varied, feeding on worms and small snails, as well as insects, crustaceans, bivalves, plant matter and occasionally small fish (4).

With an extremely large range and a relatively large population, the dunlin is not at immediate risk of extinction. However, there are a great number of threats to this species, with the loss of its breeding habitat through afforestation particularly problematic (5). 

In the winter, this species is restricted to a small number of estuaries, so it is vulnerable to any changes in this habitat, for example through land reclamation and the invasion of alien plant species. Important migratory stop-over habitats on the Baltic Sea coastline are also threatened by petroleum pollution, wetland drainage for irrigation, peat-extraction, reedbed mowing and burning, and changing land practices which lead to scrub and reed overgrowth (5). 

The dunlin has also been extensively hunted in the past, although this is now a lesser threat (2), and it is susceptible to avian influenza (5). In some areas, introduced predators such as the hedgehog (Erinaceus europaeus) have greatly reduced the breeding success of this species (6).

In North America, the dunlin is protected by the North American Migratory Bird Treaty Act of 1918, which protects this species and its eggs from hunting and collection (2). In the UK, this species is also well protected in Special Protected Areas, with around 74 percent of the total breeding population found in such reserves (6). 

A conservation priority for the dunlin is the development of monitoring across its range so that overall population trends may be determined (2).

Find out more about the dunlin:

• Avibirds European Birdguide Online - Dunlin:
  http://www.avibirds.com/euhtml/Dunlin.html