Marine Wildlife Encyclopedia
Dunlin Calidris alpinus
In winter, flocks of dunlins create a breathtaking spectacle, as they wheel in the thousands over coastal feeding grounds. Up close, the dunlin is a typical calidrid wader, one of over two dozen similar species that feed on coasts worldwide. It has a compact body, narrow wings, a tapering tail, and a black, finely pointed bill. Its plumage is variable, but breeding males usually have a black patch on the underside, which fades when they molt. Dunlins mainly eat small crustaceans and mollusks that live just beneath the surface of the shore. When feeding, they usually stay close to the water’s edge, alternately pecking into the mud or sand, and then running forward at high speed. Dunlins breed in the Arctic and subarctic, where they nest in a range of habitats from moorland to tundra, often some distance inland. Both parents help to incubate the eggs and raise the young. After breeding, dunlins gather in flocks to migrate to warmer coasts, but rarely travel into the Southern Hemisphere. Other members of this genus include many other flock-forming species, such as the red knot and sanderling, most of which travel as far north as the Arctic Ocean to breed.
Wintering waders form some of the largest bird flocks to be found on coasts. Flocking makes it harder for predators to approach unseen and helps young birds to locate good feeding sites by following adults. Some waders, such as the purple sandpiper and ruddy turnstone, frequently form mixed flocks.