Familiar to beachgoers throughout North America, Sanderlings run up and down the beach with the surf. Like the Red Knot, they undertake very long migratory journeys from the Arctic to South America, though some stay to spend the winter along the Gulf Coast. The Sanderling is still a common bird, but Gulf Coast Christmas Bird Count data show a slow but steady decline since the 1960s. Like other birds that feed on beaches, Sanderlings are threatened by contaminated prey or reduced prey abundance, lingering oil, disturbance, and reduced habitat quality.
During most of the year, Sanderlings are quite pale. White below and gray above, with black legs and a black bill, the birds are about 8 inches long. As the breeding season approaches, however, the Sanderling's back, head and neck redden significantly, particularly in males, which attain a darkly speckled, rufous color.
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; 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.
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, three or four 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 4 weeks of 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 20 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.
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