Appearance

Information scattered and conflicting. Few molt data and only some plumage data for S. m. albididorsalis, and Escalante (1985) offered first and so far only brief description of molt (of primaries only) in austral S. m. maxima, so what follows refers to boreal S. m. maxima unless otherwise indicated. In general, Royal Tern molts poorly understood, with enormous individual and probably population variation, so only “standard” sequence (if such exists) described. In some gulls, molt may be almost continuous, a cautionary tale for students of tern molt.

In boreal S. m. maxima, molts variable, complex, overlapping, frequently suspended, partial, and inconsistent even within single population; plumages follow suit. Sources used (with modifications): Cramp 1985 and Malling Olsen and Larsson 1995, both of which provide exhaustive detail. Austral S. m. maxima skins from Uruguay (Escalante 1985) suggest completion of Prejuvenal molt in Feb, of Prebasic in May, and of Prealternate in Sep, but data preliminary only. Sexes alike in all plumages.

Hatchlings

Highly variable; described in detail in Breeding: young birds, above.

Juvenal Plumage

Acquired by Prejuvenal molt while young still in crèche, but no published information on its progress.

Juvenal plumage variable and when fresh, can be close to “no two alike,” especially when bare parts considered. Forehead, lores, and crown white, with variable black spots/streaks; nape and ear-coverts black; back gray, scapulars and gray tertials with subterminal brown-black spots and fringed with white-buff; back, rump, upper tail-coverts, and tail dark gray; remiges gray but appearing dark at distance; wing-coverts variably dusky gray, with brownish greater-coverts showing as variable carpal bar. Underparts of body uniformly white, sometimes lightly tinged gray. Underwing white, except dusky tips to remiges, especially secondaries; tail usually dusky-tipped and quite short. Entire plumage heavily subject to darkening and fading from wear and sun, respectively, through first winter, most noticeable on primaries, secondaries, tertials, and rectrices.

Basic I Plumage

Acquired by complete Prebasic I molt, beginning Sep–Nov of first calendar year with head, back, scapulars, greater-coverts, and central pair of rectrices; head, body, and remaining coverts usually renewed by Jan–Feb; rectrices Sep to Apr–May; primaries Nov–Jan to Aug–Oct.

Basic I plumage similar to Definitive Alternate plumage except as follows: upperparts dark gray, some individuals with dark gray bar across lesser upper wing-coverts which eventually wears away, plus dark tertials and dark subterminal bar on secondaries; tail short with dusky tips; retained gray Juvenal primaries quickly wear/bleach to very dark brown; forehead, lores, crown white with dark occipital band connecting both eyes. Bleaching and wear lead to blotched feathering over entire body by late winter.

Alternate I Plumage

Acquired by incomplete Prealternate I molt, beginning Apr–May with head, central rectrices; tail completes Dec–Jan, but entire molt erratic and sometimes suspended.

Alternate I plumage similar to Definitive Alternate plumage except as follows: forehead white, crown spotted, and crest short; lesser wing-covert bar usually lost while dark secondary bar retained even into third calendar year; and Juvenal primaries gradually replaced. Dark-brown unmolted Juvenal outer primaries and wing-coverts often contrast with fresh pale inner primaries and up to 3 remix generations can be present. Mixed rectrices also common, with reduced tail-band as tail gradually lightens.

Subsequent Subadult Plumages

Prebasic II and Prealternate II molts poorly understood, and current information regarding timing and extent of these molts incomplete and speculative (not based on marked individuals of known age). Plumages resulting from these molts appear to be intermediate between Basic I and Alternate I and Definitive plumages but these subadult plumages probably individually variable, with some more closely resembling Definitive plumages and others more closely resembling Basic I and Alternate I plumages (Cramp 1985, Malling Olsen and Larsson 1995).

Definitive Basic Plumage

Acquired by complete Definitive Prebasic molt beginning with upperparts Jul–Aug to Feb (except head May–Jun to Sep), rectrices Aug–Dec; primaries Jul–Jan (or until Apr). Definitive Basic plumage as Definitive Alternate, but forehead, lores, crown white; black mask connects eyes via shortened occiput/crest; variable numbers of unmolted remiges and rectrices dark and worn (tail thus shorter than in Definitive Alternate).

Definitive Alternate Plumage

Acquired by partial Definitive Alternate molt; head, some body-feathers (Feb–Mar).

Definitive Alternate plumage with forehead, lores, crown, shaggy crest, and nape glossy black; underparts, underwings, side of head, and neck bright white; Upperparts pale gray, lightening toward rump and upper tail-coverts, with tail essentially white. Tail forked, with rectrices progressively elongated toward outermost pair. Primaries pale gray with silvery bloom to outer webs. Tips and inner webs and of secondaries and tertials white-edged. Great variability in color of primaries, secondaries, tertials, and rectrices from wear and bleaching, ranging from silvery gray through dark gray to brown and almost black.

Bill And Gape

In downy chicks, bill yellow-orange through pink to olive green, any color having black tip or not. Adult’s bill strong orange-yellow or orange (exceptionally crimson, close to Caspian Tern [Millington and Reid 1995]; apparently reddish bills more common in austral S. m. maxima and Cayenne Tern [Escalante 1985, R. Escalante pers. comm.]). Juvenile’s bill normally same color it showed as a chick, gradually changing through winter to pale yellowish orange (sometimes almost yellow; rarely reddish-yellow) and darkening with age. Fully orange bill usually not attained until Definitive Alternate plumage but kept thereafter, paling somewhat in winter. No information on gape color.

Iris

At all ages very dark brown to black.

Feet And Legs

In downy chicks, from pink to yellow-orange to greenish to black; also bicolored with any of preceding in blotches of varying extent and location. Juvenile retains downy leg color, gradually becoming brighter yellow with age until blackish patches appear on tibia, upper tarsal surface, and toes. By May–Jul of summer following hatch, feet and legs largely black (yellow or sometimes pink soles retained). Thereafter, entire foot and leg black, but previous light color retained on soles permanently.