Sanderlings are well known to many beach goers as the quick little white birds that run around at the water's edge, picking at the sand and retreating frantically up the beach just beyond the reach of each new breaking wave. Most people see Sanderlings only in migration and over the winter; in summer, they are on their breeding grounds in the high Arctic, thousands of miles from most of North America's popular beach destinations!
During most of the year, Sanderlings are quite pale. White and gray, overall, with black legs and a black bill, the birds stand about six inches tall. As the breeding season approaches, however, the Sanderling's back, head and necks darken significantly, particularly in males, which attain a darkly speckled, rufous-colored head and neck. Sanderlings are plump but small, weighing approximately 2 ounces and measuring just 8 inches in length, with a 17-inch wingspan.
This species breeds high in the Canadian Arctic, from Southampton Island at the north end of Hudson Bay, and throughout Nunavet, Victoria Island and Banks Island. It also breeds in areas along Alaska's north coast, east from Barrow. Nonbreeding populations occur in summer far south of the breeding range. In winter, this long-distant migrant is likely to be found on just about any beach throughout the Americas, as far north as British Columbia and Nova Scotia, and south as far as Chile and Argentina. Outside of North America, the species breeds in northern Greenland, Norway, and Siberia and winters widely across the southern hemisphere. Less than half of the world's Sanderling population resides in the Americas.
On its breeding grounds beyond the Arctic Circle, the Sanderling prefers low, rocky tundra, either coastal or near lakes or ponds. During the rest of the year, it is found almost exclusively on beaches. It generally prefers sandy, wave-swept coastlines, but can also be found on rocky shorelines, or in wetlands. During migration, it is occasionally found far inland, along lakeshores or on mudflats.
In winter and during migration, Sanderlings feed frequently in the narrow area where ocean meets sand; each receding wave leaves behind a wealth of nourishment, and Sanderlings specialize in finding it before the next wave breaks! Food items include small mollusks and crustaceans, crab eggs, aquatic invertebrates, worms, and insects. On the breeding grounds, where Sanderlings inhabit tundra and pond edges, larval and adult insects are the main food taken. Prey such as flies, mosquitoes, spiders and moths make up the bulk of the species' diet here. Plant material may also be eaten when necessary.
Sanderlings arrive on their Arctic breeding grounds in late May and early June. Here, they pair off quickly and begin nesting. The female selects the site, but no actual nest is constructed. Instead, 3-4 earthen-colored eggs are laid directly on the ground. Female Sanderlings will sometimes lay two clutches of eggs, in which case the male will tend to the first while the female cares for the second. After about four weeks' incubation, the chicks hatch. Within 12 hours, the downy young birds will begin to wander from the nest site and are capable of feeding themselves. The parents stay with their chicks for at least twenty days, at which point the young birds are already able to fly. Adults depart the breeding grounds early, leaving young birds to migrate on their own.
Sanderlings are long-distance migrants. From the Arctic breeding grounds in summer, some North American individuals will migrate "only" a few thousand miles to the coast, while others move considerably further, all the way to the lower regions of South America. Birds that migrate further south spend practically their entire lives moving back and forth from one end of the globe to the other, resting only briefly on the wintering grounds, then briefly again to breed in the north. Timing and routes of Sanderling migration are poorly understood.
MacWhirter, B., P. Austin-Smith, Jr., and D. Kroodsma. 2002. Sanderling (Calidris alba). In The Birds of North America, No. 653 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Richards, Alan. 1988. Shorebirds - A Complete Guide to Their Behavior and Migration. Gallery Books. New York.
