94 A MANUAL OF THE BIRDS OF AUSTRALIA, 
this colour increasing in extent and becoming pale towards the tips; the inner 
primaries and secondaries grey on the outer webs, fringed and tipped with white 
on the inner ones, the white increasing in extent on the secondaries ; tail for the 
most part grey like the back with a certain amount of white on the inner webs of 
the feathers ; lores, hind-neck and upper mantle, throat and entire under-surface 
silky-white, including the axillaries, under wing-coverts, and under tail-coverts ; 
bill reddish-orange ; iris dark brown ; feet black. Total length 420 mm.; culmen 
50, wing 308, tail 152, tarsus 26. 
Adult female—Similar to the adult male. 
Adult in winter —Differs from the breeding-plumage in having nearly the whole 
of the head white, with the exception of a black spot in front of each eye, a few on 
the crown, and the nape feathers, which are black, more or less fringed with white ; 
bill pale in colour. 
Immature.—Fore-head white, on top of head nape black former with white 
edges as in winter, but darker ; wing-coverts grey with brown edges ; secondaries 
brownish-grey and inner secondaries brown, but with long white edging ; primary- 
coverts brown-grey ; primaries brown with scant greyish bloom ; tail-feathers with 
long brown edges and tips, bases grey ; legs brown mottled with yellow. 
Nestling—Does not appear to have been described. 
Nest.—A slight depression in the sand or coral. 
Eggs—Clutch, one ; ground-colour light stone, blotched or spotted with very 
dark purple, with lavender ones appearing as if beneath the surface ; axis 54.5 mm., 
diameter 35-36. 
Breeding-season—November. (South Barnard Island.) 
Distribution and forms.—From the Red Sea, on the Indian coasts, through 
Malaysia to Northern Australia. Three subspecies may be recognised : P. b. bengalen- 
sis (Lesson) from India (exact range undetermined) ; P. b. arabicus (Mathews), from 
the Red Sea, is a paler and smaller race ; and P. b. torresii Gould is also paler and 
smaller (with which P. 6. robini (Mathews) is included). A fourth is indicated by 
Sterna zimmermanni Reichenow (Orn. Monatsb., Vol. XI., p. 82, 1903), from Kiaou- 
tschou, but diagnosis indeterminate and no specimens available. Under the latest 
ruling of the Nomenclatural Laws, the subspecific arabicus Mathews is inadmissible, 
being a synonym of the typical race, so we rename the Red Sea race Pelecanopus 
bengalensis par nom. nov. 
Genus GELOCHELIDON. 
Gelochelidon Brehm, Vogel Deutschl., p. 771, (pref. July) 1831. Type (by monotypy) : 
G. meridionalis Brehm = Sterna nilotica Gmelin. 
Laropis Wagler, Isis, 1832, heft 11, col. 1225, Nov. Type (by monotypy): S. anglica 
Montagu = S. nilotica Gmelin. 
Larger Terns, with short stout bill, long wings, short tail, and long legs. The 
diagnostic features of this genus are the short stout bill and short tail with feet 
with webs incised. The metatarsus is longer than the middle toe and claw, but 
shorter than the culmen, which is also shorter than the head. The tail is deeply 
forked, but still less than half the length of the wing. 
Coloration as in Sterna, etc. 
68. Gelochelidon nilotica.—GULL-BILLED TERN. 
[Sterna nilotica Gmelin, Syst. Nat., Vol. I., pt. m., p. 606, April 20th, 1789: Egypt, North 
Africa. Extra-limital.] 
Gould, Suppl., pl. 81 (pt. m1.), Sept. Ist, 1859. Mathews, Vol. II., pt. 3, pl. 104, Sept. 20th, 
1912. 
