Appearance

Black belly and rich, rufous dorsum of breeding plumage are diagnostic. The following descriptions are from Bent 1927, Holmes 1966c, Cramp and Simmons 1983, and Haymen et al. 1986 unless otherwise stated. Plumage differences among North American races slight; difficult to separate under field conditions. For pterylography of C. a. pacifica and C. a. arcticola, see Holmes 1966c .

Hatchlings

Covered with down; underparts whitish, breast tinted yellowish buff; head yellowish buff, paler on cheeks, and back yellowish tawny; both patterned with blackish brown, the dark parts of the back thickly sprinkled with minute, round spots, terminal tufts of pale buff; a distinct stripe of these nearly encircles the posterior half of the crown. Head with dark line from top of bill to crown, and crown mottled dark blackish and yellowish-tawny. Dark streak from side of bill to eye, and small moustache streak. Nape a mixture of dull buff and dusky; back mottled dark and light (Gabrielson and Lincoln 1959). Overall, much paler and more buffy than Least or Western sandpipers.

Juvenal Plumage

Prejuvenal molt complete, begins replacing down beginning first week; flight and contour feathers fully grown at 4–5 wk (C. a. arcticola) (Holmes 1966c), but some down retained on occipital and auricular regions (C. a. pacifica) throughout this period (REG). Plumage fleeting and variable in overall richness.

Appearance superficially like that of adult (Alternate plumage) with crown dusky, throat whitish, neck and chest rich buff and finely streaked gray, sometimes black as Alternate. Abdomen white but marked to variable extent with small black spots or blotches, sometimes giving appearance of black belly patch on breeding adults. Mantle and scapulars black, narrowly fringed cinnamon buff; tips of feathers of outer mantle and outer scapulars white, sometimes forming double chevron on back. Tertials dull dark gray, fringed buff to cinnamon, with black subterminal mark. Back and rump dark gray, uppertail-coverts black, feathers tinged cinnamon buff on tips. Wing and tail as Alternate, but central rectrices narrowly fringed buff, otherwise mostly off-white (C. a. pacifica).

Basic I Plumage

Prebasic I (Postjuvenal) molt incomplete; flight feathers, most wing-coverts, and some feathers on humeral tract and interscapular region retained; usually begins late Jul (C. a. pacifica) and early Aug (C. a. arcticola) before Juvenal plumage fully grown (Holmes 1966c). Completed on wintering grounds (California) into Dec (Page 1974, contra Holmes 1966c).

Plumage similar to Definitive Basic plumage (see below) except wing-coverts and secondaries buff-edged (contra Paulson 1993); flight feathers generally more worn, especially obvious in spring.

Alternate I Plumage

Acquired by partial Prealternate I molt that includes most body feathers but variable. In C. a. pacifica, body molt begins as early as late Feb in California (Holmes 1966c, NDW); Apr in Washington (Paulson 1993). In California, 1.8% of adult and 4.7% of second-year (immature) birds molting tertials in Mar and Apr (Page 1974). Body molt scores shown to differ between sites as close as 12 km apart (Ruiz et al. 1989).

Definitive Basic Plumage

Definitive Prebasic molt (C. a. arcticola and C. a. pacifica) begins on breed-ing grounds in late May, early Jun (Holmes 1966c). Primaries, beginning with innermost, molted every few days until P10 molted; generally completed mid-Aug, but 8% of birds captured on Alaska Peninsula, AK, after 22 Sep (n = 230) still molting P8–10 (REG). Secondaries, beginning with outermost (S1), rectrices, and body feathers replaced between late Jun and mid-Sep (Holmes 1966c, REG). Body feather molt completed on wintering grounds by Dec (Page 1974). Prebasic molt of flight feathers usually completed at northern staging areas; rarely on wintering grounds (unlike European races of Dunlin; see Holmgren et al. 1993b), but in C. a. hudsonia at Rasmussen Lowlands, Northwest Territories, and La Pérouse Bay, Manitoba, active wing molt on incubating and migrating birds; at Churchill, Manitoba, primaries molted in Jul, very little body molt (late Jun–early Aug) (C. Gratto-Trevor pers. comm., J. Jehl pers. comm.).

Overall drab gray-brown upperparts and breast. Central forehead, crown, sides of head and neck, hindneck, mantle, scapulars, and tertials gray, slightly tinged buff (especially on neck); shafts blackish, centers of longer feathers darker gray; when fresh, feathers narrowly tipped white. Supercilium and eye-ring white. Back and central rump grayish black with gray fringes, central uppertail-coverts black with narrow white fringes, sides of rump and lateral uppertail-coverts white. Chin white; foreneck, chest, sides of breast, and upper flank pale gray with slight buff tinge, shafts sepia-black. Remainder of underparts white with some narrow dark gray or black streaks on breast, lower flanks, or undertail-coverts (streaks or small dots extend finely to rearmost flank feathers in C. a. hudsonia). Tail and wing as in Definitive Alternate. Black shafts of crown, mantle, upper scapulars, foreneck, and chest more distinct when plumage is worn. Sexes similar.

Definitive Alternate Plumage

Definitive Prealternate molt partial, occurs late Feb through early May. Similar to Prealternate I molt but central rectrices replaced in some adults (Holmes 1966c). Head (except crown), neck, breast, and tail light gray, shading into white below and ashy on tail; head, neck, breast, and flanks slightly spotted and streaked, crown rusty and black. Feathers on mantle black, evenly fringed rufous cinnamon; narrowly tipped pale gray or off-white when fresh; scapulars bright rufous cinnamon when fresh, often with pale gray tips. Back and central rump grayish black with gray fringes, central uppertail-coverts black with narrow white fringes, sides of rump and lateral uppertail-coverts white. Axillaries and most underwing-coverts white. Flight feathers gray, shading to black on outer webs and tips of outer 3–4 primaries. P1–6 with white border to basal and middle portions of outer web. Primary-coverts black, tipped white; greater upperwing-coverts dark gray with broad white tips. When wing is open, white-tipped greater and primary coverts, and white-based secondaries and inner primaries form white wingbar (Haymen et al. 1986). Large patch on midbelly uniform black. In C. a. pacifica, streaking on underparts ends sharply, forward of black belly-patch; in C. a. hudsonia, breast streaking butts onto black belly-patch, without an intervening white band, and continues on flanks and as fine shaft-streaks on undertail-coverts. Fringes of upperparts on C. a. arcticola brighter and deeper red than in other 2 North American races.

Bill

Black or brown-black (adult and juvenile); dusky (downy young).

Iris

Dark brown.

Legs And Feet

Black sometimes slightly tinged olive or deep gray (adult and juvenile); dark gray (downy young).