(2089) Sterna albifrons pusilla.
Sterna pusilla Temm., Man. d'Orn., 2nd ed., iv, p. 464 (1840) (Java). Sterna minuta. Blanf. & Oates, iv. p. 321 (part.).
Vernacular names. None recorded.
Description. In this little Tern the first primary shaft is light brown, the second darker brown; the upper tail-coverts and tail are almost concolorous with the grey back and the bill is very small.
Colours of soft parts as in the other races.
Measurements. Wing 160 to 175 mm.; culmen 26 to 30 mm.: average 29 mm.; much more slender than in the preceding two races.
Winter and juvenile plumage differ from that of the adult in the same way in all the races. The small bill suffices to distinguish this form from both S. a. albifrons and S. a. sinensis and its pale brown primary shafts from the black-shafted S. a. saundersi.
Distribution. The great rivers of Northern India and Burma, rare in the South of India and not extending to Ceylon. In Burma it is found throughout the country on suitable waterways and thence through the Malay Peninsula to the Celebes and Philippines.
Nidification. This Ternlet differs from all others in breeding on rivers only and not on the sea-coast. The rivers selected are, almost without exception, the larger rivers with wide free stretches of sandbanks in their beds. The birds do not breed in large colonies ; as a rule some twenty to thirty pairs but, occasionally, as many as two or three hundred may be found together. The nest-scrapings are generally placed very close together, sometimes a dozen nests in three or four square yards. One hundred eggs average 30.9 x 23.2 mm.: maxima 32.9 x 23.0 and 30.8 x 24.4 mm.; minima 28.0 x 23.3 and 31.1 x 21.4 mm. The eggs differ from those of the two preceding races not only in their much smaller size but also in being, as a series, less heavily blotched. The breeding-season is also different, as the young have to be hatched and reared before the Rains break and flood the rivers in which they breed; accordingly, most birds lay in early March and April.
Habits. Except that it keeps to big inland rivers its habits are much the same as those of other Ternlets. Its food consists of small fish, freshwater prawns and small shellfish.