Sterna sinensis Gmelin, Syst. Nat. (1788), 1, pt. 2, 608. Saunders,
Cat. Birds Brit. Mus. (1896), 25, 113; Sharpe, Hand-List (1899),
1, 136; Oates, Cat. Birds' Eggs (1901), 1, 192; McGregor and
Worcester, Hand-List (1906), 21.
Luzon (Whitehead); Mindanao (Steere Exp.); Mindoro (Bourns &
Worcester); Palawan (Whitehead). Chinese and Indian seas to
Australia.
"Adult male in breeding plumage.--Lores black from base of bill to eye;
forehead as far as a little beyond the top of eye white; crown and nape
black; mandible pearl-gray; secondaries bordered with grayish white;
shafts of primaries pure white in the outer, and pale gray in the
upper ones; outer web of the outer primary and a broad line next the
shaft on its inner web dark gray; on the succeeding primaries paler
gray; upper portions and edges of inner webs white; rump pearl-gray;
tail and under parts white. Bill gamboge-yellow, tipped with black;
tarsi and feet orange-yellow. Length, 280 when the streamers are
fully developed; culmen, 35; wing, 188; tail, 145; depth of fork,
86; tarsus, 16; middle toe with claw, 20.
"Adult female.--Slightly smaller than the male and with less developed
tail-streamers.
"Adult in autumn.--Similar, with more white on the forehead, and
shorter tail-streamers; primaries darker on their terminal portions,
owing to the disappearance of the frosting, until the new quills
appear.
"Immature.--Like the above, but dull white on crown and the front
of the lores; primaries still darker, the outer shafts always white,
the other shafts dusky; upper wing-coverts dark gray; tail-feathers
grayish, and the streamers not much prolonged; bill dark brown,
tarsi and toes ochraceous.
"Young.--Forehead buffish white, crown with black streaks which
become confluent on nape; upper parts mottled and barred with buffish
brown on a dull gray ground. Bill horn-color; feet ocher-yellow. When
the bird is barely fledged the buff-color predominates on the upper
surface." (Saunders.)
"Found by us in great abundance near the center of Mindoro, where it
was flying about over the dried beds of streams and alighting among
the pebbles, its color assimilating so closely with that of the sand
and small stones that it was well nigh impossible to see it on the
ground." (Bourns and Worcester MS.)