(2084) Sterna hirundo tibetana.
THE TIBETAN TERN.
Sterna tibetana Saunders, P. Z. S., 1876, p. 649 (Tibet). Sterna fluviatilis. Blanf. & Oates. iv, p. 318 (part).
Vernacular names. Dao-kekra (Cachari).
Description. Differs from the preceding race in being slightly darker both above and below, a distinction which is very apparent if breeding birds from Tibet are compared with breeding birds of the typical race.
Colours of soft parts as in the preceding race.
Measurements. Wing 245 to 279 mm.; tail 145 to 156 mm.; tarsus about 19 to 22 mm.; culmen 34 to 38 mm.
Birds in Winter plumage and young birds are indistinguishable from the preceding race.
Distribution. Ladak, Tibet and Central Asia.
Nidification. The Tibetan Tern breeds on the great lakes and some of the rivers of Ladak, Tibet and Central Asia, its nest and eggs being exactly like those or! the Common Tern, though the latter do not vary to the same extent. At present, however, there are but few of them known and larger series might show-greater variation. A series of forty-five collected for me on the Hramtso Lake in Tibet are nearly all of the dull brown or grey-green type and in size average 41.9 x 30.5 mm. : maxima 47.4 x 31.1 and 42.2 x 32.2 mm.; minima 39.1 x 30.0 and 41.0 x 29.0 mm. These were all taken from a colony breeding in Tibet at 12,500 feet, and they breed from this elevation up to at least 15,000 feet. I was informed that the birds made quite substantial nests of reeds and rubbish and did not lay their eggs on the bare mud-flats which surround these lakes. My series were taken about the 26th of June but at this time many young had been hatched and the eggs sent were all advanced in incubation. In North-East Chihli La Touche obtained ten eggs in July from the coast.
Habits. The Tibetan Tern is a very common visitor to the whole of Western and Central India, wandering as far South as Ceylon. It occurs throughout Burma and also in the Malay States. It is impossible to distinguish Winter and young birds of this race from the Common Tern, so that records are very mixed hut there is little doubt that the whole of our Eastern records should apply to this bird only. The Tibetan Tern is as much, or more, a lake and river Tern than a coastal bird and keeps to the larger rivers, where it may be seen fishing in the shallows, either singly or in pairs or small flocks. In flight, voice and diet it differs in no way from the Common Tern.