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 MS.)
Genus STERNA Linnæus, 1758.
Bill much as in Hydrochelidon but somewhat longer; toes completely
webbed; tail always distinctly forked; outer rectrices usually much
longer than the others.
Species.
a1. Crown black.
b1. Larger; wing, 240 mm. or more.
c1. Forehead black to base of culmen.
d1. Larger; tarsus yellow or red; bill red in summer. ... hirundo
(p. 89)
d2. Smaller; tarsus blackish, bill black at all
seasons. ... longipennis (p. 89)
c2. Forehead white.
d1. Lores white. ... boreotis (p. 90)
d2. Lores black.
e1. Wing, 265 mm.; mantle umber-brown. ... anæstheta (p. 91)
e2. Wing, 300 mm.; mantle deep black. ... fuscata (p. 92)
b2. Smaller; wing less than 200 mm. ... sinensis (p. 92)
a2. Crown white. ... melanauchen (p. 93)