The appearance of the spotted sandpiper varies dramatically. The picture shown is in non-breeding plumage, but you can see the strong breeding plumage in this shot.
These are extremely common birds, nesting throughout the Northern United States, and can often be noticed from a distance by their repeated bobbing motion. They walk a few steps, bob up and down, look for food, and then do it again. No one seems to know why they do this, but it certainly helps birders in the field know whether they've got a spottie.