The semipalmated sandpiper, Calidris pusilla, is a small bird named for the webbing present between its toes (Terres 1980). Despite its somewhat nondescript coloration, the species is used as a standard for identification of sandpipers. Distinguishing characteristics include a thick black bill and black legs (Paulson 2005). Both sexes are similar in appearance, differing mainly in bill size and shape. Male bills are short and blunt, while the longer bills of females have a tapered and slightly drooped form (Farrand 1983). Plumage and body coloration vary with age and season, and descriptions are divided accordingly below. Breeding Adult Plumage varies from grayish-brown to mottled brown and black upperparts with an occasional reddish tint (Paulson 2005). The brow feathers (supercilium) and throat are conspicuously white, and the head is marked on each side with a brown loral (between the eye and bill) stripe. The breast usually bears several brown stripes and dots, and the sides of the body are often streaked with brown.Non-breeding Adult Plumage is gray-brown with fine, dark streaks at the shaft of the feathers (Paulson 2005). The supercilium and loral stripes are similar to those of breeding adults. Juvenile Legs are olive, darkening to black during the fall migration (Paulson 2005). Plumage coloration is quite variable, but most individuals are brownish with feathers fringed in tan and tipped with white, giving the birds a scaled appearance. Breasts of the youngest individuals are tan, fading to white during the first migration.