On August 26, 2013 I came upon a small group of Western Sandpipers along the south edge of Soap Lake in Grant County. Among them I spotted a Semipalmated Sandpiper. I stayed with them for quite a while, filling my digital camera card with image after image.
Later, while processing the images, I noticed that the semi and one of the westerns shared poses in several of them. Here are those images. In some shots the dark green legs of the semi are visible and in others, the black legs of the western. Bills, structure and plumage may also be compared.
These 2 species can at times drive one to drink. ID can be extremely challenging if not impossible. Semi on the left and western on the right.