(2071) Hydroprogne caspia caspia.
THE CASPIAN TERN.
Sterna caspia Pall., Nov. Com. Acad. Sci. Petrop., xiv, p. 582 (1770) (Caspian Sea). Hydroprogne caspia. Blanf. & Oates, iv, p. 309.
Vernacular names. Kekra (Sind).
Description. - Breeding plumage. Upper part of head black from forehead to nape, including crest; hind-neck white; upper parts pale grey, the rump, upper tail-coverts and sail almost white; primaries darker brown-grey, frosted with silver-grey when new, the inner webs with a pale median line and dark edges and tips; remainder of plumage white.
Colours of soft parts. Iris dark brown or hazel; bill coral-red, in Winter duller with a dusky tip; legs and feet black.
Measurements. Wings 380 to 421 mm.; tail 130 to 153 mm.; tarsus about 43 to 48 mm.; culmen 64 to 72 mm.
In Winter the black on the head is replaced by white streaked with black and the white collar on the hind-neck is more conspicuous.
Young birds have no black head and the feathers of upper parts are partly grey barred with brown, especially on the scapulars, inner coverts and innermost secondaries; the tail-feathers and primaries are darker.
Young in down. Above greyish or buffy-white, faintly freckled with dusky black ; below white, buffy-white on the fore-neck.
Distribution. Europe, North to lat. 60°, Northern Africa, Western Asia ; in Winter to India, Burma and Ceylon.
Nidification. Within Indian limits the Caspian Tern breeds only on the Mekran coast and perhaps some of the adjacent islands, as it also breeds on many islands in the Persian Gulf. On the Sonmeani Bheel Ludlow obtained a fine series of clutches consisting of two and three eggs each. The nests were fairly substantial structures of sticks, rushes and reeds built on the top of the scrubby bushes which grew everywhere on the marsh. No eggs were laid on the ground in this colony but in the Persian Gulf islands they sometimes make nests on the sand and rocks. The eggs vary in colour from a very pale stone to a fairly warm buff but the range is very poor. The markings consist of blotches of dark brown, reddish-brown or purplish-brown, sometimes small but generally of some size and occasionally large and bold. The secondary marks are of grey and purplish neutral tint. Thirty Indian eggs average 64.8 x 46.0 mm. as against 64.0 x 44.5 mm. in one hundred European eggs.
The breeding-season in India and the Persian Gulf is June and the eggs are of ten destroyed by the intense heat, the half-incubated chicks being killed by the sun if left too long by the parents. It has also been found breeding in Ceylon on the sand-banks of Adam's Bridge.
Habits. When not breeding the Caspian Tern is generally seen singly or in pairs, flying slowly and lazily over big rivers and lakes, hunting for the fish and prawns upon which it feeds. It has a loud harsh cry which the natives of Sind syllabify as " kekra."