Appearance

Hatchlings

Account based on Fjeldså 1977, except as noted. Newly hatched chicks are chubby; average mass 10–12 g, length 95 mm; bill horn-colored, with dusky tip; iris dark brown; legs and feet grayish yellow, with some dusky spots. Newly hatched chicks completely downy; upperparts dull, blackish brown with very little buff (especially rufa), abundantly speckled with rows of white (sometimes cinnamon) dots, with rudimentary hourglass pattern, but with more prominent white bands of loose, large “powder puffs” to each side; wing-pads often with diffuse “powder puffs,” white at tip. Dark median crown runs from bill to eye; partial stripes run below eye; superciliary zone densely mottled with black; prominent mottles and lines on cheek and ear regions, and as a line across occiput. Chin white, with white patch on either side (R. S. Palmer in Stout 1967). Coloring becomes lighter gray on sides, and then light on underparts, with buffy-grayish wash on breast.

Juvenal Plumage

No information on timing or sequence of Prejuvenal molt. Juvenal plumage similar to Definitive Basic plumage in overall ap-pearance (see below), but dorsal contour feathering (wing-coverts, scapulars, mantle) and rectrices with buff outer margin, bordered internally by parallel dark band. Sides of upper breast suffused with buff and marked with fine brown streaks and dots instead of bars (Paulson 1993). Upperparts tinged slight olive to ash gray, subtly darker than in Definitive Basic plumage. Sexes alike (R. S. Palmer in Stout 1967).

Basic I Plumage

Prebasic I molt partial; includes head- and body-feathers (except back to upper tail-coverts only occasionally replaced), some rectrices (occasionally all or none), and sometimes a few tertials or median upper wing-coverts. Molt begins early Sep–late Oct and ends late Oct–Dec. Some birds wintering in Southern Hemisphere replace inner, outer, or all primaries Jan–Jul (Cramp and Simmons 1983); see description of Definitive Basic plumage, below.

Basic I plumage similar to Definitive Basic plumage (see below), except for presence of retained Juvenal feathers.

Alternate I Plumage

Prealternate I molt partial and extremely variable in extent. Some individuals replace only a few feathers (especially those summering within Tropics), while in others, molt is similar in extent to Definitive Prealternate molt. In w. Europe, throat, upper breast, side of breast, scattered head-feathers, upper back, scapulars, and occasionally upper tail-coverts, some scapulars, much of belly, and many median upper wing-coverts replaced. Molt occurs Apr–Jun, ending when Prebasic molt begins with P1 (Cramp and Simmons 1983).

One-year-old knots, which replace few feathers, appear as winter, Basic-plumaged birds during their first boreal spring and summer (Belton 1984, Blanco et al. 1992) but typically have highly worn and frayed primaries. Individuals that molt more extensively show rufous feathering below (Paulson 1993) but are generally intermediate in appearance between Definitive Basic and Definitive Alternate plumages (Cramp and Simmons 1983).

Definitive Basic Plumage

Definitive Prebasic molt complete; timing of molt varies between subspecies. In Europe, may begin on breeding grounds with scattered feathers on chin and body, but most molt occurs after southward migration begins, earl-ier in islandica (late Jul–late Aug) than in canutus (mid-Aug–mid-Sep, or not until Oct–Nov). In both of these subspecies, body molt becomes heavy with loss of P1, and all body-feathers, secondaries, and rectrices replaced when P10 fully grown, about 2.5 mo after loss of P1. One-year-olds initiating this molt for the first time molt earlier, at least in w. Europe, where molt begins late May–mid-Jul with loss of P1, completing with P10 from late Jul or (in South Africa) from Jul to Dec (Prater et al. 1977, Cramp and Simmons 1983).

Southward-migrating individuals in Massachusetts during Jul and early Aug (mostly rufa bound for Austral wintering grounds) show molt of ventral and dorsal body-feathers, but do not show any flight-feather molt. Body-feather molt appears to become arrested before departure in mid-Aug (BAH). A few adults captured later than Aug in New England and many caught in southeastern states show advanced Prebasic molt of primaries, secondaries, and rectrices. This flight-feather molt appears to be virtually completed before these knots, perhaps roselaari, move to Floridian winter locations during Oct and Nov (BAH).

During Dec, 114 of 119 C. c. rufa photographed in Argentina were actively molting primaries with molt gaps about midway between proximal and distal feathers; virtually all (95%) were in Basic plumage, and the balance probably were juveniles (Morrison and Harrington 1992). This stage of primary molt was equivalent (see below) to that observed among knots on Georgia (U.S.) coast during mid-Sep (BAH).

In contrast to northeastern states, knots in se. Atlantic states during Aug and Sep (possibly roselaari) show Prebasic molt of ventral and dorsal body-feathers, as well as actively molting primaries and rectrices (BAH).

Following description is adapted largely from Witherby 1924 . Basic plumage dull white ventrally, plain ash gray above (crown, mantle, tail, and scapulars), with thin, light fringes (when plumage is fresh) on scapulars and median wing-coverts. Feather shafts dark. White tips on greater upper wing-coverts and inner primary-coverts, giving appearance of a white line running the length of the wing (as is true for virtually all Calidris) when in flight. Under wing, rump, lower back, and axillary feathers light gray, some with dark, subterminal, irregularly shaped chevrons. Upper breast dirty white, with fine, brown wavy bars that may extend laterally to flanks. Supercilium, chin, throat, and sides of neck light gray. Primaries dark brown to black on outer webs, paler on inner webs, shading to white at base; proximal primaries with light borders on outer webs. Distal primary-coverts and alula dark brown-black. Secondaries and tertials and remaining greater and lesser wing-coverts ash gray, broadly tipped with white. Rectrices gray with narrow white fringes, outer rectrices often with dark subterminal band. Sexes alike.

Definitive Alternate Plumage

Definitive Prealternate molt partial; in European populations, includes head, neck, underparts (often not all feathers in males), back, scapulars (scattered Basic scapulars sometimes retained), sometimes part of back and rump (mainly in males), usually some or all upper tail-coverts, usually 2–3 inner or longer tertials and some or all tertial-coverts, none to about half of median upper wing-coverts (occasionally some lesser wing-coverts), often R1, and sometimes r2. Molt begins late Feb–mid-Mar, with heavy molt in Apr, and completes by early May.

Male. Variation occurs in North American populations. Description here focuses on C. c. rufa (BAH). Crown and nape streaked with black and gray and/or salmon; prominent superciliary stripe brick red or salmon red, auricular region and lores colored as in crown but with finer streaks; chin, throat, breast, flanks, and belly brick red or salmon red, sometimes with a few scattered light feathers mixed in; undertail white, often including scattered brick-red or salmon-red feathers, marked with dark, terminal chevrons laterally. Back-feathers and scapulars with dark brown-black centers, edged with faded salmon. Scapulars and tertials unevenly colored, with broad, dark, irregular-shaped centers, widely edged in notched patterns to variable degrees, some with faded salmon and others with bright salmon-red color. Lower back and upper tail-coverts barred black and white, with scattered rufous (Paulson 1993). Remiges, rectrices, and about half of wing-coverts retained from Basic plumage. Primaries dark brown to black, secondaries and remiges gray. Putative younger males tend to be less brightly colored dorsally (BAH) and have greater numbers of light feathers scattered among ventral feathering (Hobson 1972). Underwing duller than in other Calidris, with smudges gray axillaries and coverts (Cramp and Simmons 1983).

Female. Similar to male, but with salmon colors typically less intense, tending toward buff or light gray dorsally. Superciliary stripe less pronounced than in most males, sometimes indistinct from crown and eye-line area hindneck buff rather than cinnamon. Underparts usually less brightly colored than in male; include scattered white feathers (retained from Basic plumage according to Cramp and Simmons [1983]). Sometimes females also have scattered breast- and/or flank-feathers with wavy, dark marks at tips (BAH).

Bill

In adults and juveniles, black year-round (BAH).

Iris

Dark brown.

Legs

In adults, dark gray-black, sometimes dark olive-gray in putative subadult knots (BAH). In juveniles, greenish gray.