Rhynchops nigra, Linn. Syst Nat. vol i. p. 228.—Lath. Ind. Ornith. vol. ii. p. 802.—Ch. Bonaparte, Synopsis of Birds of United States, p. 352.
Black Skimmer, or Shear-water, Rhynchops nigra, Wils. Amer. Ornith. vol. vii. p. 85, pl. 60, fig. 4.—Nuttall, Manual, vol. ii. p. 264.
Adult Male. Plate CCCXXIII.
Bill longer than the head, nearly straight, tetragonal at the base, suddenly extremely compressed, and continuing so to the end. Upper mandible much shorter than the lower, its dorsal outline very slightly convex, its ridge sharp, the sides erect, more or less convex, the edges approximated so as to leave merely a very narrow groove between them; the tip a little rounded when viewed laterally. Nasal groove rather short, narrow near the margin; nostrils linear-oblong, sub-basal in the soft membrane. Lower mandible with the angle extremely short, the dorsal outline straight or slightly decurved, the sides erect, the edges united into a very thin blade which fits into the narrow groove of the upper mandible, the tip rounded or abrupt when viewed laterally.
Head rather large, oblong, considerably elevated in front. Neck short and thick. Body short, ovate, and compact. Feet short, moderately stout; tibia bare below, with narrow transverse scutella before and behind; tarsus short, moderately compressed, anteriorly covered with broad scutella, reticulated on the sides and behind; toes very small; the first extremely short, and free; the inner much shorter than the outer, which is but slightly exceeded by the middle toe; the webs very deeply concave at the margin, especially the inner. Claws long, compressed, tapering, slightly arched, rather obtuse, the inner edge of the middle toe dilated and extremely thin. Plumage moderately full, soft, and blended; the feathers oblong and rounded. Wings extremely elongated, and very narrow; the primary quills excessively long; the first longest, the rest rapidly graduated; the secondaries short, broad, incurved, obliquely pointed, some of the inner more elongated. Tail rather short, deeply forked, of twelve feathers, disposed in two inclined planes.
Bill of a rich carmine, inclining to vermilion for about half its length, the rest black. Iris hazel. Feet of the same colour as the base of the bill, claws black. The upper parts are deep brownish-black; the secondary quills, and four or five of the primaries, tipped with white; the latter on their inner web chiefly. Tail-feathers black, broadly margined on both sides with white, the outer more extensively; the middle tail-coverts black, the lateral black on the inner and white on the outer web. A broad band of white over the forehead, extending to the fore part of the eye; cheeks and throat of the same colour; the rest of the neck and lower parts in spring and summer of a delicate cream-colour; axillary feathers, lower wing-coverts, and a large portion of the secondary quills, white; the coverts along the edge of the wing black.
Length from point of upper mandible to end of tail 20 inches, to end of wings 24 1/2, to end of claws 17; to carpal joint 8 1/4; extent of wings 48; upper mandible 3 1/8; its edge 3 7/8; from base to point of lower mandible 4 1/2; depth of bill at the base 1; wing from flexure 15 3/4; tail to the fork 3 1/2; to end of longest feather 5 1/4; tarsus 1 1/4; hind toe and claw 4/12; middle toe 10/12; its claw 4/12. Weight 13 oz.
The female, which is smaller, is similar to the male, but with the tail-feathers white, excepting a longitudinal band including the shaft.
Length to end of tail 16 3/4, to end of wings 20 1/4, to end of claws 16 1/4, to carpus 8; extent of wings 44 1/2. Weight 10 oz.
After the first autumnal moult, there is on the hind part of the neck a broad band of white mottled with greyish-black; the lower parts pure white, the upper of a duller black; the bill and feet less richly coloured.