The western sandpiper, Calidris mauri, is one of a few Florida shorebirds belonging to a group known as 'stints' (small sandpipers belonging to the genera Erolia or Calidris). Distinguishing characteristics include a black bill and legs (Paulson 2005). Like similar species, sex can be determined in part by bill length. In general, female bills measure at least 2.5 cm longer than those of males (Paulson 2005), a difference thought to be derived from intersexual competition for food at wintering locations (Stein et al. 2008). Plumage and body coloration vary with age and season, and descriptions are divided accordingly below. Breeding Adult Reddish-brown plumage of varying degrees is concentrated on the crown, ears and along the upper back (Paulson 2005). The breast is streaked, and the sides are marked with several black streaks and chevrons. In the fall after breeding, individuals are often faded and patchier. Non-breeding Adult Coloration is nearly identical to that of the semipalmated sandpiper, C. pusilla. Plumage is plain grayish-brown above and white below, the eyebrow feathers (supercilium) are white and the breast is lightly streaked (Paulson 2005).Juvenile Legs are olive, darkening to black in adults (Paulson 2005). Plumage coloration on the head is similar to that of non-breeding adults, but darker and more distinct. Wing feathers are grayish-brown to reddish-brown with buff fringes. Underparts are mostly unmarked, and the sides of the breast are streaked. Breasts of the youngest individuals are tan, fading to white during the first migration.
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