Several species of sandpipers resemble C. pusilla at first glance. Of these, the western sandpiper, C. mauri, and the least sandpiper, C. minutilla, are most likely to overlap in range. The bill of the western sandpiper is usually longer, thinner and more drooped than that of C. pusilla (Farrand 1983; Paulson 2005). Plumage is very similar between the species, except in breeding adults where the head of the western sandpiper is reddish-brown and sides are distinctly marked with chevrons. The least sandpiper is easily distinguished from C. pusilla upon close examination, characterized by paler legs, shorter wings and browner coloration (Paulson 2005). When plumage and body coloration are similar among species, the semipalmated sandpiper can be identified with practice by its distinct call (see 'Voice' below) (Farrand 1983). Flight Patterns & Locomotion: While in flight, semipalmated sandpipers form close flocks with a uniform twisting motion that reveals their dark backs followed by the white of their breasts. Flight speeds of some individuals have been recorded up to 50 mph (Terres 1980). Flocks settle on the ground and spread out to feed, running just above the wave line on beaches, in shallow water or on exposed tidal flats (Terres 1980; Collazo et al. 2002). While resting, flocks often huddle closely. Individuals orient into the wind with their bills buried in their back feathers, and frequently stand or lightly hop on one leg (Terres 1980).