(2072) Gelochelidon nilotica nilotica.
THE GULL-BILLED TERN.
Sterna nilotica Gmelin, Syst. Nat., i, p. 606 (1789) (Egypt). Sterna anglica. Blanf. & Oates, iv, p. 311 (part.).
Vernacular names. None recorded.
Description. - Breeding plumage. Upper part of head from forehead to hind-nape, including lengthened feathers of nape, velvet-black; upper plumage pale pearl-grey; first primary grey-brown with a long white wedge-shaped mark on the inner web ; remaining primaries grey, browner on the inner webs with decreasing wedge-shaped white patches and darker tips; remaining plumage pure white.
Colours of soft parts. Iris brown; bill, legs and feet black tinged with blood-red, this tinge being lost in Winter.
Measurements. Wing 287 (exceptional) to 333 mm.; tail 121 to 148 mm.; tarsus 33 to 37 mm.; culmen 35 to 41 mm.
In Winter the black head is lost, but the white is often streaked with black and a patch of streaky black round the eye and over the ear-coverts nearly always persists.
Young in first plumage have the upper parts, especially the scapulars, inner wing-coverts and innermost secondaries pale brown with huffish edges ; the crown is grey or greyish-white and the primaries are darker.
Distribution. Europe as far North as lat. 55°; Northern Africa, Western Asia to India, Ceylon and Burma. In India it breeds in many places in the North-West, Kashmir and probably Ceylon, whence birds have been obtained in full breeding plumage. It occurs over the greater part of Burma and probably breeds on the bigger rivers but its eggs have not actually been taken.
Nidification. The Gull-billed Tern breeds within our limits freely on the larger rivers of North-West India from the Frontier on the Indus to the Gogra in Oude. It has been found breeding in Ceylon, on the Godavery and the Ganges but not farther East. The eggs are laid on sand-banks in the larger rivers and on the shores of lakes and swamps as at Sonmeani on the Mekran coast-. The normal full clutch is two or three and the eggs are laid in scratchings in the sand with no pretence at a nest. The eggs vary a good deal; the ground-colour ranges from pale yellowish or greenish stone to a rich warm buffy-brown and they are marked with large blotches of brown, purple-brown or reddish-brown, underlying which are others of grey and lilac One hundred Eastern eggs average 47.9 x 34.2 mm.; maxima 51.5 x 37.0 mm.; minima 43.5 x 34.0 and 47.0 x 32.4 mm. This bird breeds from April to the middle of* May in small colonies, seldom over 40 or 50 couples.
Habits. This Tern is probably resident wherever found, though there may be an influx of migrants in the North-West during the Winter. It frequents the larger rivers, swamps and lakes and is never seen in very large flocks and often singly or in twos and threes. It feeds on insects, small fish, mollusca and, like so many Terns and Gulls, is especially fond of grasshoppers.