Appearance

Molts, especially of flight feathers, are timed to occur between the periods of greatest energy expenditure—breeding and migration. Wing and tail molt typically occur after fall migration but may be initiated on breeding grounds (shortest primaries only) and then arrested during fall migration. Prebasic body molt occurs primarily after but in part during fall migration, and Prealternate body molt occurs primarily before but in part during spring migration. Clearly the birds’ energy balance allows migration and at least some body molt simultaneously.

Hatchlings

Completely downy. Upperparts and thighs yellow, heavily marked with black flecks concentrated peripherally to form incomplete dark edge; supercilium only sparsely marked with black. Complete collar and underparts white, including sides above thigh feathers.

Juvenal Plumage

See Breeding: young birds, for Prejuvenal molt. Crown, back, scapulars, and tertials dark brown, moderately to heavily spotted with yellow or whitish, former fading rapidly to whitish. Pale spots arranged in series around borders of scapulars and tertials. Crown spots vary from scarcely evident to almost obscuring brown ground color. Back and sides of neck streaked brown and grayish white. Wing-coverts medium brown, paler than back, widely fringed with pale yellow or white. Rump coarsely barred brown and yellowish. Uppertail-coverts white, in most with narrow brown bars and shaft streaks. Rectrices barred dark brown (7–9 bars) and white, brown bars slightly to much wider than white ones; in some, white bars tinged with yellow distally.

Forehead, anterior lores, and sides of head whitish, finely streaked with brown, streaks heavier in auricular region in some individuals; preocular spot brown. Underparts white, variably streaked with brown, at minimum involving neck and upper breast, at maximum (exceptionally) involving entire underparts except center of belly. Undertail-coverts white, outer ones with fine brown streaks and bars.

Wing brown above, prominent stripe formed from white markings on outer webs of inner 5–7 primaries. Secondaries slightly paler than primaries. Primary-coverts dark brown, darker than rest of wing, and fringed with white only near tips. Greater underwing-coverts light gray-brown, fringed with white at tip; median-coverts pale gray-brown to white; lesser-coverts white, may or may not be heavily marked with medium to dark brown. Bases of inner webs of primaries white. Axillars black.

Basic I Plumage

Prebasic I molt. Surprisingly variable. Typically most of body plumage replaced but not tertials and many coverts, late Sep through at least early Nov (Boere 1976, B. Harrington and S. Groves pers. comm.), but some individuals with only crown and some mantle feathers replaced at end of Dec.

Replaced feathers as in Definitive Basic. By early spring, pale tertial markings mostly worn off, but tertials look ragged compared with still-intact tertials of adults; primaries and tail very worn.

Alternate I Plumage

Prealternate I molt partial to complete body molt in Apr–May into plumage essentially like Definitive Basic or, to varying degrees, with increasing proportion of Alternate-like feathers to extreme indistinguishable from Definitive Alternate. Males apparently more likely than females to achieve Definitive Alternate appearance in first year. One to 3 innermost pairs of rectrices usually molted in males, perhaps not in females.

Basic Ii Plumage

Prebasic II remigial molt in Pacific Northwest late May through Jul (Paulson 1993), in England as in Definitive Prebasic molt but begins early in summer (supposition), finishes by mid-Sep, 2 mo earlier than in adults (Branson and Minton 1976). Plumage identical to Definitive Basic but details of body molt unsure; presumably complete. Small proportion migrate south in second year without having undergone wing molt, presumably remigial molt schedule as adults.

Definitive Basic Plumage

Definitive Prebasic molt complete. Some body molt on breeding ground (Van Tyne and Drury 1959, Parmelee et al. 1967). Body molt lengthy in Washington, some in molt on arrival in Jul, most in molt Aug–Sep, remnants of Alternate still present on few in late Oct (DRP). In Netherlands, body molt begins in Aug, heavy through Oct and completed in Nov (Boere 1976). Apparently some body molt takes place during migration, as most arrive in Venezuela in full Basic (McNeil 1970).

Remigial molt in England well studied (Branson and Minton 1976). Continuous in most adults but seasonal placement variable, begins late Jul to mid-Sep, complete late Sep to late Nov; presumably correlated with greatly varying arrival times. Begins with loss of P1, then P2–P5 lost in turn before P1 begins to grow; P6 lost only after substantial growth of inner feathers, P7 lost after P1–P4 fully grown; thus 5 or 6 inner primaries often growing simultaneously early in molt, 2 or 3 later. Average duration of primary molt 90 d.

Arrested molt in 25–40% of adults captured in Netherlands in Aug; in these birds, 1–3 (mode 2) inner primaries replaced, presumably on breeding grounds, then molt stopped, to resume on wintering grounds, e.g., in Morocco (Pienkowski et al. 1976). Failed breeders may be more likely to accomplish this molt. Arrested molt of outer primaries also in about 16% of adults after mid-Nov, perhaps unable to complete at that time; remaining primaries not replaced until at least following spring (Branson and Minton 1976). Even higher proportion in arrested molt through winter in Netherlands, where some outer primaries apparently retained for >1 yr, generating 2 molt cycles in wing (Boere 1976). Secondaries and tail in some birds also show arrested molt, finish in late winter or early spring (Boere 1976).

No evidence from North America contradicts this scenario; most wing molt occurs Aug–Oct. Rather well-synchronized molt through P7 in mid-Sep in Washington (DRP). Primary molt in 43% of 192 adults captured in Massachusetts in autumn. Additional 16% in arrested molt, with 1–3 (mode 1) inner primaries replaced. Proximal and distal molt wave in 3 birds, believed to be in second year. Birds molting primaries remained longer than those not in molt. At least some molting secondaries and/or rectrices (B. Harrington and S. Groves pers. comm.). Molt apparently occurs during migration in Massachusetts, as too few winter there to account for large numbers captured in molt.

Drab brownish gray to dark brown above, including rump, most feathers narrowly fringed with pale gray-brown. Tertials sparsely and narrowly barred with dark brown and/or with alternating darker and lighter dots or notches along their edges. Wing-coverts gray-brown with white fringes and notches. Pale areas of head less heavily streaked than in juvenile. Breast and sides vary from pure white through grayish to fairly heavily mottled with brown; foreneck with brown streaks or, rarely, heavily flecked with dark brown on neck, breast, and sides. In few extreme individuals underparts almost entirely brown; otherwise, underparts white. Rectrices white with dark bars, differing by sex: in males, bars dark brown to black, narrower and often fewer (4–7) sometimes lacking on outer rectrices; in females, bars brown, wider and often more (6–8), distal white areas often tinged brownish. Wings as in Juvenal plumage

Definitive Alternate Plumage

Definitive Prealternate molt incomplete. Virtually complete body molt in males, not including many feathers associated with wings: axillars, primary-coverts, most greater and lesser and some median secondary-coverts, probably underwing-coverts, and in some, a few tertials. Much less complete and more variable in females, at maximum many feathers, in all tracts, retained from Definitive Basic.

Migration apparently begins before molt complete or even begun in some birds (McNeil 1970). Full Alternate attained by few individuals by end of Mar in California (Michael 1935). Earliest feathers of Alternate visible by end of Mar in Pacific Northwest, as many as 10% of birds in nearly full Alternate by first week of Apr (DRP). Single males in apparently full Alternate observed 9 Dec in Argentina (A. Jaramillo pers. comm.) and 15 Jan in Washington (DRP).

Sexually dimorphic. Male with vivid white stripe on either side of neck running from front of crown to wing. Crown pale gray, in palest individuals scarcely distinct from neck stripe, with scattered black spots to rear or heavily marked with black in some. A few males with crowns about as dark as females. Mantle, scapulars, and tertials black with white tips and notches on feathers, looking vividly barred. Alternate plumage assumed by a varying number of secondary-coverts, at maximum all of medians, scattered lessers, and 1–3 innermost greaters, all of which vividly barred black and white: remainder of wing-coverts retained from Definitive Basic. Lower back gray-brown, variably barred with black. Uppertail-coverts white with fairly narrow black bars. Throat, foreneck, breast, and upper belly solid black; lower belly and undertail-coverts white. Outermost undertail-coverts with few well-defined black spots. By southbound migration in Jul, dorsal white feather tips may have worn so much as to be almost absent, much darker-backed accordingly. Rectrices and remiges retained from Definitive Basic.

Females vary from almost as bright as males to markedly different, apparently a combination of less complete Prealternate molt and duller plumage. Head and neck stripe in some distinct, in others not apparent. Crown varies from light gray-brown as in Definitive Basic, with little crown-mantle contrast, to fairly heavily marked with dark brown; never entirely whitish as in male. In plainest females, mantle, scapulars, tertials, and coverts drab gray-brown, fringed with paler gray. Much more plumage change apparent in some, with scapulars and/or tertials heavily barred with dark brown to blackish, but never as vividly black-and-white looking as male because ground color darker. Lower back gray-brown with whitish fringes, uppertail-coverts white with light to heavy brown barring. In most extreme individuals, underparts largely black except for lower belly and undertail-coverts, but black usually mixed with white, often to extent of being thoroughly mottled or even largely white below. Outer undertail-coverts often more heavily marked than in male, with dark brown to black spots. As in male, remiges and rectrices retained from Definitive Basic.

Bill

Grayish black in 5-d-old chick, bill and gape black from just-fledged juveniles (Parmelee et al. 1967) throughout life.

Iris

Dark brown.

Legs And Feet

Hatchling gray (DRP), 5-d-old chick grayish black, freshly fledged juveniles dark olive gray (Parmelee et al. 1967), juveniles and nonbreeding adults medium to dark gray, breeding adults black.