Identification

Medium-sized, bulky Calidris sandpiper (total length about 23–25 cm; average mass 135 g, range 85–220 g; wingspan 45–54 cm) usually found foraging and roosting in large flocks at localized, traditionally used marine sites in non-breeding seasons. Characteristic calidridine profile: proportionately small head, small eyes, short neck, short tibia, stout tarsus, straightish bill tapering steadily from a relatively thick base to a thinner tip, bill length not much longer than head length; when feeding, typically probing in a hunched posture, though long, tapered wings give the body an elongated, streamlined profile when standing upright or flying. During non-breeding season, found principally in sandy or muddy intertidal, marine habitats, especially near coastal inlets, estuaries, and bays, or along restinga formations (a rocky intertidal shelf, of variable surface roughness, in places with a rich invertebrate fauna) in South American non-breeding and migration areas.

Alternate plumage distinctive; face, neck, breast and much of the belly of C. c. rufa are characteristically a somewhat faded salmon-red to brick-red color, with a light-colored lower belly behind the legs, including the vent and under tail-covert region. C. c. rogersi very similar, but with more coloration on lower belly and under tail-covert region. C. c. islandica more richly colored, with redder hues than rogersi or rufa, and with slightly shorter bills, on average. Upperparts , including back feathers, axillaries, and tertials of all 3 races generally have dark brown- black centers, with rufous and grey edges; the resulting spangled appearance provides effective camouflage on the arctic tundra nesting areas. Males are usually somewhat more brightly colored than females, with more extensive rufous, especially on the underparts). Flight feathers grade from dark brown/blackish in the primaries to grey in the secondaries, and there is a narrow whitish wingbar. Tail feathers are grey. Females have less distinct eye-lines and the underparts may appear somewhat lighter rufous, sometimes with dark, subterminal markings, which occur less frequently in males.

Basic plumage undistinguished; similar between sexes and among subspecies. Plain gray above , with light fringes (when plumage is fresh) on scapulars and median wing coverts, white tips to greater wing coverts giving the appearance of a white line running the length of the wing (as is true for virtually all Calidris) when in flight. Rump and lower back feathers dull white, with dark subterminal chevrons. Underparts dirty white, with faint, dark vertical streaking on upper breast that may extend laterally to the flanks. Head dull grayish with a whitish supercilium. Juveniles have characteristic dark sub-terminal bands on the feathers of the mantle, scapulars and coverts, which may present a scaly appearance when fresh, though most sub-terminal bands are lost through abrasion by the end of the first winter. Juveniles may also show a pale pinkish-buffish color suffusing the breast when plumage is fresh. Bill black, legs typically dark gray to black, but yellow and sometimes greenish in juvenile and some older birds.

In Basic plumage, most easily confused with Basic-plumaged dowitchers (Limnodromus spp.) but may be distinguished by shorter bill, paler crown, whitish rump barred with grey (versus a white lower back forming a distinctive “V” in dowitchers) and voice. Basic-plumaged Dunlins (Calidris alpina) distinguished by their smaller size, and proportionately longer bill with down-curve at tip; also darker gray dorsum.

Basic plumage recalls larger Great Knot (C. tenuirostris), but rump white barred grey appearing uniform grey with rest of upperparts, and white wingbar more marked.