Common Sandpiper (Actitis hypoleucos), left, photographed in Sept in Malaysia by Alister Benn and Spotted Sandpiper (Actitis macularia), right, photographed in Iowa by Kent Nickell in Aug Spotted Sandpiper has a shorter tail projection, plain tertials (these are streaked on the edges in Common) and yellower legs. In flight, Common has a distinclty longer white wing bar. Thanks to Paul Van Gasse, Kruibeke, Belgium for this id info