Appearance

Natal Plumage

Precocial, completely covered with down. Upperparts pale grayish buff, irregularly and sparsely spotted with black. Underparts immaculate white (Bent 1921).

Juvenal Plumage

Complete. Sexes alike. Feathers begin to appear about day 7; birds fully feathered by day 15–18. Upperparts buffy brown, each feather with black center and broad buff edging. Lores and suborbital region uniform pale buff, the former however with a dusky space in front of eye. Greater wing coverts blackish gray or tipped with white. Secondaries whitish, primaries blackish, P5–P8 margined with buff. Primaries 1–4 dusky, becoming white at tip. Underparts whitish (Ridgway 1919). Buff feather edgings fade to whitish soon after fledging.

Basic I Plumage

Partial body molt, completed by Jan. The head becomes dark brown, faintly mottled with white, and bordered by a clear white nuchal collar, which shades gradually into the new sooty-brown mantle and scapulars or contrasts abruptly with them. In winter and spring the dark upperparts contrast sharply with the lighter brown Juvenal median and greater coverts, from which the white fringes have virtually worn off. On specimens examined, replacement of Juvenal wing coverts and flight feathers had not begun by mid-Mar.

Extent and timing of first Prealternate molt is unknown, but individuals with a white nuchal collar and molting wings and tail in the midst of the breeding season are likely to be in Alternate I plumage or molting into Definitive Basic plumage.

The age at which skimmers normally first achieve Definitive Basic and Definitive Alternate plumages and first molt in synchrony with older individuals is unclear. Birds with at least a few white feathers on the hindneck in breeding season may not have completed primary molt by late Aug.

Definitive Basic Plumage

Complete; sexes alike. For some individuals Pre-basic molt begins on the breeding grounds with 1–3 primaries; otherwise it apparently takes place in winter quarters and has been completed by Jan except for the flight feathers, which may have been completely replaced as early as mid-Mar or as late as early Jun. Flight feather molt slow and protracted as in African Skimmer (Cramp 1985); thus Bent (1921) and Oberholser (1974) mistakenly believed that skimmer replaced flight feathers twice per year.

Similar to Alternate plumage (see below) except browner cast to upper parts and a broad whitish nuchal collar. Pre-alternate molt of both second-year birds and adults begins in early spring (Feb–Mar) resulting in blacker upperparts and loss of nuchal collar.

Definitive Alternate Plumage

Incomplete body molt; no flight feather molt. Sexes alike. Feb through May (Forbush 1925, van Rossem 1945, Oberholser 1974; contra Bent 1921). Typically involves most to all dorsal plumage and underparts; the white nuchal collar in Definitive Basic plumage is replaced with black.

Mainly sooty black above, including auriculars, forehead, suborbital and malar regions; underparts pure white. Secondaries edged white; underwing coverts and axillars sometimes pale gray with possible geographic variation (Wetmore 1944, van Rossem and Hachisuka 1937). Rectrices white, except middle pair grayish brown edged with white. Outer web of rectrices narrowly to broadly edged with white (may be age-related).

Bill

Dusky pinkish with dark dusky tip in Juvenals, becoming brownish black by first winter. Black in adults with basal half of bill vermilion red to orange red.

Legs And Feet

Dusky pinkish in Juvenals becoming dull dusky reddish by first winter and orange vermilion in adults (Ridgway 1919).

Iris

Dark brown.