Distinguishing Characteristics

Medium-sized, slender, long-legged shorebird (230–250 mm from bill- to tail-tip, 590–640 mm wingspan, 67–94 g body mass). Sexes similar in plumage and overall size, but females have slightly longer wings on average. In Alternate (breeding) plumage, upperparts mottled gray-brown, white, and black. Underparts white with brown streaking on neck and breast and irregular, blackish barring on anterior flanks. In Basic (nonbreeding) plumage, upperparts uniform gray to gray-brown with pale spots (most evident on wing-coverts). Under-parts white with fine gray streaking on neck and breast. Autumn juveniles resemble Basic adults but browner above with more regular and profuse pale spotting on upperparts and indistinct streaking on breast. First winter birds separated from adults by pale versus dark brown notching on tertials (Prater et al. 1977).

In all plumages, distinguished from most other North American shorebirds by slender body, long neck, and long, bright-yellow legs. Often confused with Greater Yellowlegs but about 25–30% smaller in total length and has a thin, straight bill that is only slightly longer than head. Greater’s bill is thick at the base, often perceptibly upturned, and about 1.5 × head length. Also, Lesser’s bill is dark in all seasons, in contrast to Greater’s, which is often two-toned (grayish at base) in nonbreeding birds. In Alternate plumage, markings on Lesser’s breast and flanks are sparse relative to Greater’s heavily barred and spotted underparts. In Juvenal plumage, streaks on breast and neck are paler and more blurred in juvenile Lesser than in juvenile Greater (Hayman et al. 1986). Voice is diagnostic in all seasons and often the most reliable field mark; typical call of Lesser consists of 1–3 notes (usually 2) that are lower pitched, more rapid, and much less resonant than the Greater’s characteristic 3–4-note call (Rowan 1929, Wilds 1982). Less obvious differences between the 2 species include the Lesser’s unmarked secondaries, proportionately longer legs, and smaller leg joints (Hayman et al. 1986, Paulson 1993).

Other tringine sandpipers that could be confused with Lesser Yellowlegs include Solitary Sandpiper (T. solitaria) and Wood Sandpiper (T. glareola), but the former, which occurs throughout most of Lesser Yellowlegs’ range, is darker above (including dark rump) and has greenish legs and a conspicuous white eye-ring; the latter, a rare migrant and occasional breeder in Alaska, has shorter wings (projecting only to tail when standing), greenish- or brownish-yellow legs, a pronounced supercilium that extends behind as well as in front of the eye, and a distinct high-pitched, whining call (Tree and Kieser 1982). Other species that are similar in appearance when in Juvenal or Basic plumage include Wilson’s Phalarope (Phalaropus tricolor) and Stilt Sandpiper (Calidris himantopus), but the former has shorter legs, an extremely fine bill, and lacks streaking on head, neck, and upper breast. The latter has plain (Basic) or fringed (Juvenal) upperparts, greenish legs, a complete supercilium, and a bill that droops at the tip (Hayman et al. 1986, Paulson 1993).