302 BRITISH BIRDS. 



Genus CENTURA. 



The Spine-tailed Swifts were included by Linnseus in the genus Hirundo 

 with the other Swifts and the Swallows. From the latter the Swifts were 

 separated as early as 1777 by Scopoli; and in 1835 Stephens placed the 

 Spine-tailed Swifts in a new genus^ which he called CtuBtura (Shaw's Gren. 

 Zool. xiii. pt. 3j p. 76). The American Chimney- Swallow {C. pelasgia), 

 the first enumerated by Stephegs^ has been generally accepted as the type. 



The Spine-tailed Swifts may be at once recognized by having the shafts 

 of the tail-feathers prolongated like needles or spines beyond the web. 

 The tail is very shorty considerably less than half the length of the wing, 

 and the wings are very long and powerful. Unlike the true Swifts, in the 

 foot of the Spine-tailed Swifts three toes are directed forwards and one 

 backwards. The plumage of the upper parts is generally glossed with 

 metallic purple and green. 



Sclater (Proc. Zool. Soc. 1865, p. 607) enumerates fifteen species 

 belonging to this genus, of which seven belong to the Neotropical and 

 two to the Nearctic Region ; three breed in the Oriental and two in the 

 Ethiopian Region ; whilst one breeds in the Palsearctic, winteriug in the 

 Australian Region. One species is an accidental visitor to Europe and 

 the British Islands. 



The Spine-tailed Swifts are gregarious, chiefiy frequenting open 

 country, and living almost entirely on the wing. Few, if any, birds exceed 

 them in the rapidity of their fiight. They feed exclusively on insects. 

 They breed in hollow trees, holes in rocks, or in chimneys, using no mud 

 in the construction of their nests, but cementing the materials, which 

 consist of straw, hay, or twigs, with their glutinous saliva. The eggs are 

 few in number and dull white in colour. 



