COLLOCALIA. 175 



Length about 4-25 ; tail 1-5 ; wing 4-2 ; tarsus -4. The under 

 tail-coverts extend nearly to the end of the tail. 



Distribution. The forest country from Bengal to the Godavari 

 and west as far as the Wyne Gunga, also Seoni in the Central 

 Provinces, Garhwal and Sikhim in the Himalayas, the Wynaad, 

 and Coonoor in the Nilgiris. Widely spread but local. 



Habits, <$fc. A forest species, generally seen in smaller or larger 

 parties hawking insects amongst high trees, especially near streams, 

 or frequenting open cultivated spaces in the jungle. The flight is 

 not, I should say, much more rapid than that of the Palm-Swift. 

 Nidification unknown. 



1080. Chaetura leucopygialis. The Grey-rumped Black Spine-tail. 



Acanthylis leucopygialis, myth, J. A. S. JB. xviii, p. 809 (1849) ; id. 



Cat. p. 85 ; id. Ibis, 1866, p. 339. 



Acauthylis eoracinus, Mull. Bonap. Consp. Av. p. 64 (1850). 

 Chsetura coracina, Sclater, P. Z. S. 1865, p. 614; Hume, S. F. iii, 



p. 318 ; Hume % Dav. S. F. vi, p. 45. 

 Chsetura leucopygialis, Hume, S. F. vii, p. 518 ; id. Cat. no. 95 bis ; 



Hartert, Cat. B. M. x\i, p. 490. 

 Rhaphidura leucopygialis, Oates, B. B. ii, p. 6. 



Coloration. Black, with a bluish gloss throughout, above and 

 below, except the rump and long upper tail-coverts, which are 

 greyish white (pearly grey) with narrow black shafts. 



Bill black ; irides dark brown ; legs and feet livid purple. 



Length about 4*75 ; tail 1'7 ; wing 4'9 ; tarsus *4. The upper 

 tail-coverts extend to the end of the webs of the tail-feathers ; the 

 naked shafts of the latter project -3 to -4 inch. 



Distribution. The extreme south of Tenasserim, ranging through- 

 out the Malay Peninsula to Sumatra and Borneo. 



Habits, 6fc. very similar to those of C. sylvatica, but by Davison's 

 account this appears to be a swifter bird. 



Genus COLLOCALIA, Gray, 1840. 



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 as- 

 certained 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 de- 

 rived 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 



