Sterna anæstheta Scopoli, Del. Flor. et Faun. Insubr. (1786),
1, 92; Saunders, Cat. Birds Brit. Mus. (1896), 25, 101; Sharpe,
Hand-List (1899), 1, 136; Oates, Cat. Birds' Eggs (1901), 1,
190; McGregor and Worcester, Hand-List (1906), 20. Worcester,
Phil. Jour. Sci. (1907), 2, sec. A, 275, pl. 1 (nesting place).
Didicas Rocks (Worcester); Panay (Sonnerat). African and Indian
seas to China, Japan, Moluccas, northern Australian, Pacific
Islands; Gulf of Mexico, Western Indies.
"Adult in breeding plumage.--Loral stripe black; upper forehead,
crown, and nape black; shoulders slate-gray, passing into dark
grayish brown on mantle; no visible white on secondaries; primaries
umber-brown, shafts black, the 'wedges' on inner webs very narrow and
not sharply defined; rump and principal tail-feathers grayish brown
like the mantle, but the streamers white on outer and upper portions
of inner webs, and the next pair of rectrices whitish at their bases;
abdomen and breast grayish white; under wing-coverts and throat pure
white. Bill, tarsi, and toes black, the inner webs of the latter
considerably excised. Length, 355 to 380; culmen, 45; wing, 262;
tail, 190; depth of fork, 102; tarsus, 20; middle toe with claw,
30. The sexes are alike in plumage.
"Adult in winter plumage.--Similar to the above, but the lores and
crown mottled with white for a short time.
"Immature.--Generally similar, but with more white on the head;
whitish tips to the feathers of the back, which, when fresh, are
somewhat gray; a dark line along upper wing-coverts, and less white
on outer rectrices. Full plumage is not attained until the bird is
at least two years old.
"Young.--Head streaked and mottled with brownish black; feathers of
upper parts dark brown with rufous tips, which subsequently become
paler, approaching white, and finally wear away; under parts grayish
white. Bill and toes brownish." (Saunders.)