Calidris alpina; the sanderling breeds on stony tundra's in arctic regions like Greenland, Northern Canada and Northern Siberia. In winter it migrates south, some remain on the British isles and the western European coasts while others may fly all the way down to Southern Africa. Sanderlings pass Iceland from the arctic America's to Europe and Africa in autumn and they return in spring. Along the migratory tracks individuals might stay anywhere some time. I saw a couple of sanderlings late in June mixed within dunlin flocks near Þörshöfn, eastern Iceland, with full summer plumage. It is an active bird often running around to find food. Typical is their behavior on beaches where they will run up and down the shore line with the last line of waves coming in and retreating.
As an extra I added a photo from the Wadden beeches of western Europe showing a sanderling in winter plumage.