Feet small; the hind toe directed backwards normally and only partially reversible. Tail-feathers of ordinary form and the shafts not rigid. Second quill longest; tail slightly forked. '
This genus contains the birds generally designated Swiftlets by Indian ornithologists, some of which build the " edible nests " of commerce. These nests are shaped like a half saucer, and some of them are white, glistening, and composed of a substance resembling isinglass. This was formerly supposed to be seaweed, then ascertained to be a secretion produced by the bird, and finally shown by Blyth (J. A. S. B. xiv, p. 210; Ibis, 1860, p. 323) to be derived from the bird's salivary glands, which are greatly developed in both sexes at the nesting-season. Hume showed that in the Andamans the pure white nests are always made by one species, C. francica, whilst other species use extraneous substances such as grass and feathers cemented together by the inspissated saliva, and their nests are consequently either less valuable, or, in some kinds, not worth collecting. All lay two white, very elongate cylindricoovate eggs, and make their nests in caves. During the day the birds hunt about for insects, frequently travelling great distances for the purpose ; Jerdon relates how the birds at Vingorla Rocks did not return to their roosts till 9 p.m., having been away all day. The flight is rapid. None, so far as is known,are truly migratory, though they wander over considerable distances. The genus inhabits the greater part of the Oriental and Australian regions.
Key to the Species.
a. Abdomen brown like throat and breast.
a1. Tarsi naked.
a2. No pale band across rump……………….C. fuciphaga, p. 176.
b2. A pale band across rump ……………….C. francica, p. 178.
b1. Tarsi feathered,
c2. Smaller, wing 5; pale rump-band in distinct……………….C. brevirostris, p. 177.
d2. Larger, wing 5.3; pale rump-band distinct……………….C. innominata, p. 177.
b. Abdomen white ; tarsi naked……………….C. linchi, p. 178.