Sanderling, Coos Bay, Oregon, 28 August 2011 by Greg Gillson. Flocks of small sandpipers chasing the waves in-and-out on the beach--anywhere in the world--are likely to be Sanderlings. Like wind-up toys they run in quick bursts on stiff legs.
Sanderlings are circumpolar nesters in the remote Arctic of both Siberia and Canada. They winter along nearly all the coasts of North America. But that's not all. Some birds migrate south from their breeding grounds through all continents south to southern South America, southern Africa, Australia, and New Zealand! In other words, there aren't too many places in the world where Sanderlings don't visit.
Sanderling, Coos Bay, Oregon, 28 August 2011 by Greg Gillson. In the non-breeding season they are pale gray; in the breeding season they have a brownish-red plumage. They can sometimes be mistaken for other shorebirds--even the rare Red-necked Stint. However, as you can see by the top photo, Sanderlings lack hind toes, while most other smaller shorebirds have them.
In the Pacific Northwest, Sanderlings are common on the outer beaches from August to February, less common March-May and July. A few non-breeders may be found in summer, but mostly they are absent from the last week of May to the first week of July. Rare inland, nearly all inland records are from August, during the southbound migration.