Sanderlings
General description
The sanderling is a small (circa.50 g) shorebird that has one of the most widespread distributions of all birds. It is found on nearly all temperate and tropical sandy beach throughout the world. Usually, sanderlings are observed in flocks scurrying along the water line while pecking or probing for small food items. Sanderlings are the only sandpipers that lack the hind toe and they are excellent runners. They have a straight, black bill and black legs. Appearance of sanderlings changes a lot with the seasons. In winter, both sexes appear almost white, with pale grey upperparts and white belly and abdomen. Up to the first moult, juveniles can be distinguished from adults by the distinct black and white pattern of their back feathers. During the breeding season, the back, head and upper part of the chest turn a rusty-brown colour, but the underparts stay white. Males are often of a more reddish brown than females, who tend to have a lighter, duller colour. In flight, a broad white wing-bar is clearly visible. Pictures of sanderling in different plumages (and different ages) can be found here:
Breeding system and distribution
Sanderlings are circumpolar breeders. They nest on rocky tundra in Greenland, Northern Canada and several places in Siberia. Sanderlings lay a four egg clutch, as is common in waders, in a shallow nest scrape lined with dry leaves. The majority of birds share incubation between both parents, but some are believed to be double-clutching. In this case, the female produces two clutches, the first being incubated by her male partner, the second by herself. Eggs are incubated for 22 days. After hatching, chicks are usually tended to by one parent and fledge after approximately 17-20 days.
Migration
The migration of sanderlings is one of the longest known in birds. From their breeding sites they move to the wintering grounds which stretch over almost 100o latitude, from 50 degrees North all the way down to 50 degrees South. Different breeding populations have different migration routes and wintering areas. For instance, the population breeding in Greenland use the East Atlantic flyway which comprises western Europe and the west coast of Africa. A recent ring recovery in France of a sanderling breeding in eastern Canada suggests that at least part of the Canadian population also uses this migration route. Sanderlings are very site faithful and return to almost the exact same wintering location each year.
