(2080) Sterna aurantia.
THE INDIAN RIVER-TERN.
Sterna aurantia Gray, Illus. Ind, Zool., i, pl. 69, fig. 2 (1831) (India). Sterna seena. Blanf. & Oates, iv, p. 315.
Vernacular names. Kinai (Sind).
Description. A patch below the eye white; upper part of head to below this white patch and including nape and crest black glossed with green; remainder of upper plumage French grey, paler on the rump, upper tail-coverts and tail almost white on the prolonged outermost tail-feathers and silvery-grey on the outer webs of primaries, secondaries and the outer wing-coverts; lower plumage pale grey, a streak under the black cap on the cheeks, under-wing and tail-coverts white.
Colours of soft parts. Iris brown; bill bright deep yellow, duller in Winter and with a darker tip; legs and feet red.
Measurements. Wing 260 to 280 mm.; tail 178 to 228 mm. tarsus about 20 to 22 mm.; culmen 39 to 43 mm.
In Winter the black cap is replaced by white or greyish-white, a certain amount of black nearly always showing in the cheeks and through the eye; the nape is also nearly always more or less streaked with black.
Young birds have the upper plumage, including wing and tail-feathers, edged with buffy-white and subedged terminally with blackish; the forehead and a broad supercilium are immaculate white.
Distribution. On all large rivers throughout India and Burma and throughout the Malay States to Singapore.
Nidification. The River-Tern breeds on all the larger rivers of Northern India and Burma and less commonly in the South. The colonies are sometimes of great size, numbering many hundred, the birds often breeding on sand-banks in company with other Terns, Spur-wing Plovers, Glareola lactea and the Stone-Curlew. No nest is made beyond a hollow7 scratched in the sand but this is rather unusually deep and they always select sand, not shingle, for their nesting-sites. Three is the normal full clutch, sometimes two only and more rarely four. They are on the whole dull-coloured eggs, the ground-colour pale stone or buff and the markings blotches and spots of dull brown, reddish-brown and purplish-brown with others underlying of neutral tint. In shape they are broad obtuse ovals. Two hundred eggs average 42.0 x 31.4 mm.: maxima 45.3 x 40.0 mm.; minima 38.0 x 30.2 and 40.3 x 29.3 mm.
The breeding-season is from March to April, rarely May, whilst Ticehurst found them breeding on a canal in Sind during August.
Habits. This Tern keeps entirely to our larger rivers, though it may be also found fishing on the swamps and lakes immediately in the vicinity of these. Like all Terns they give away their nesting-sites by wheeling backwards and forwards over them throughout the day, uttering their harsh cries as they fly and boldly attacking any intruder in the way of hawk, dog or even human being. Their food is almost entirely fish but they also eat small crustacea, tadpoles, water insects etc.