A Manual of Philippine Birds. Richard C. McGregor
a1. Tail more or less forked (except in Anous); bill slender; terminal portion of culmen straight or but slightly curved; angle of lower mandible not prominent. Sterninæ (p. 86)
a2. Tail even; bill stouter; terminal portion of culmen decidedly curved; angle of lower mandible distinct. Larinæ (p. 95)
Subfamily STERNINÆ.
The members of this subfamily afford no very tangible characters to distinguish them from the gulls other than those already mentioned. However, the terns are, as a rule, of more slender form and more airy and graceful flight. The wings, bill, and tail are proportionately longer and the body smaller than these parts in the gulls.
Genera.
a1. Tail more or less forked.b1. Tail but little more than one-third of wing, its outer feathers broad and rounded. Hydrochelidon (p. 86)b2. Tail much more than one-third of wing, its outer feathers narrow and pointed. Sterna (p. 88)
a2. Tail graduated; plumage sooty brown. Anous (p. 94)
Genus HYDROCHELIDON Boie, 1822.
Bill short and slender; legs and feet small; webs between the toes deeply emarginate; wings long, when closed, exceeding the tail; tail short, nearly square.
Species.
a1. Black or dark gray below (adults in summer).b1. Upper tail-coverts and tail white; under wing-coverts black. leucoptera (p. 86)b2. Upper tail-coverts and tail gray; under wing-coverts white. hybrida (p. 87)
a2. White below (adults in winter and young).b1. Tail white. leucoptera (p. 86)b2. Tail gray.c1. Rump gray like back. hybrida (p. 87)c2. Rump white (young). leucoptera (p. 86)
76. HYDROCHELIDON LEUCOPTERA (Meisner and Schinz.)
WHITE-WINGED BLACK TERN.
Sterna leucoptera Meisner and Schinz, Vog. Schweiz (1815), 264.
Hydrochelidon leucoptera Saunders, Cat. Birds Brit. Mus. (1896), 25, 6; Sharpe, Hand-List (1899), 1, 133; Oates, Cat. Birds’ Eggs (1901), 1, 174; McGregor and Worcester, Hand-List (1906), 20.
Mindanao (Steere Exp., Bourns & Worcester). Central and southern Europe to central Asia and China; Australia, New Zealand, Africa in winter.
“Adult in breeding plumage.—Head, neck, and upper back dark, glossy black; coverts on the carpal joint pure white; greater wing-coverts pearl-gray; secondaries darker, passing into slate-gray; primaries frosted with pearl-gray, which soon wears off the outer quills, leaving the webs sooty black, with a well-defined narrow whitish streak down the middle of the inner webs of the four outer primaries; shafts white; back and rump grayish black; upper tail-coverts and tail pure white; under parts deep black; vent white; flanks, under wing-coverts, and axillars black. Bill livid red; feet orange-red; webs of toes much indented. Length, 236; culmen, 28; wing, 208; tail, 79; tarsus, 19; middle toe with claw, 25.
“Adult in autumn and winter plumage.—In the latter part of July, when the molt begins (in Europe), the bird is curiously parti-colored, the new feathers of the head, neck, and under parts being white and those of the back gray (paler than in Hydrochelidon nigra). Later, the under parts, including the under wing-coverts and axillars, become white, the crown and nape being merely mottled with black; but by the following April the black color has reappeared to a considerable extent, especially in the axillars.
“Immature.—In birds which are not mature, though capable of breeding, the black of the under parts has a brownish tinge and the tail-feathers are pearl-gray, especially toward the tips. In winter like the adult.
“Young.—Similar to the winter plumage of the somewhat immature bird, but much mottled with dark brown on the upper parts, and the tail-feathers slightly darker gray with a brownish tinge toward the tips; upper tail-coverts always white.
“Nestling.—Ruddy fawn-color, mottled with black above, unspotted pale cinnamon-brown below.” (Saunders.)
“Observed and shot by us in Mindanao, where it was flying over the rice-fields.” (Bourns and Worcester MS.)
77. HYDROCHELIDON HYBRIDA (Pallas).
WHISKERED TERN.
Sterna hybrida Pallas, Zoogr. Rosso-Asiat. (1811), 2, 338.
Hydrochelidon hybrida Saunders, Cat. Birds Brit. Mus. (1896), 25, 10; Blanford, Fauna Brit. Ind. Bds. (1898), 4, 307, fig. 70 (head); Sharpe, Hand-List (1899), 1, 33; Oates, Cat. Birds’ Eggs (1901), 1, 175; McGregor and Worcester, Hand-List (1906), 20.
Luzon (Meyer, Murray, Whitehead, McGregor); Mindanao (Bourns & Worcester, Mearns); Palawan (Whitehead, Steere Exp.); Negros (Whitehead). Southwestern, central, and southern Europe to China, Malay Archipelago, Australia, Africa.
“Adult male in breeding plumage.—Forehead, crown, and nape deep black; from the gape to the nape a conspicuous white streak; upper parts slate-gray, darker on the primaries, except when these are new and frosted; shafts white; inner webs of outer pairs of primaries white on the upper and greater part of the inner webs; upper tail-coverts gray; tail-feathers gray, with white outer webs to the outside pair; chin white or very pale gray; throat gray, darkening on the lower part; breast dark slate-gray, which deepens into black on abdomen and flanks; vent and under tail-coverts white; under wing-coverts white; axillars white with a faint tinge of gray. Bill blood-red; feet vermilion, drying to orange-color; webs deeply indented, but less so than in H. leucoptera. Length, 280; culmen, 35; wing, 235 to 241; tail, 96; tarsus, 23; middle toe with claw, 29.
“Indian birds, which are probably almost sedentary, are slightly smaller in size. Some of the birds resident in South Africa are of a distinctly darker hue both above and below than northern examples; Australian specimens, on the other hand, are inclined to be paler.
“Adult female.—Similar to the male, or a trifle paler in general tint.
“Adult in winter plumage.—Upper parts of a paler gray than in the breeding season; forehead white; crown and nape streaked and mottled with black; under parts entirely white; bill and feet reddish brown.
“Young in first plumage.—Crown and nape blackish brown, mantle mottled with brown and with warm cinnamon-brown edges to inner secondaries; tail slightly mottled and edged with ash-brown; the rest like the adult in winter. By December the brown markings are considerably diminished.
“Nestling.—Down at the base of bill black, forehead ruddy fawn-color; upper parts paler fawn, mottled and streaked with black; under parts white, except the throat, which is sooty black for a few days.” (Saunders.)
“Common about the Pasig River and Laguna de Bay. Several flocks were observed in Mindanao feeding over the paddy-fields.” (Bourns and Worcester