Il6 THE WORLD'S BIRDS. 



Swifts seldom do so. Their nesting-habits vary a good 

 deal, but the nest is either a mud-built structure or 

 placed in a hole, generally speaking. They walk, or 

 rather waddle, when on the ground, instead of hopping. 



The House-Martins [Chelidon) differ from the rest 

 of the group and all other Passerine birds by having 

 the feet partly covered with white down instead of 

 scales, but these appear on the centre of the shanks. 

 Our House-Swallow (Hirttndo rustica) is found, accord- 

 ing to season, over most of the Old World, and in 

 America is replaced by the Barn-Swallow {H. horreorum), 

 which is very similar, but has all the underparts chest- 

 nut. The House-Martins are purely Old- World birds, 

 but the Sand-Martin {Cottle rip aria) extends all round 

 the world. The American Purple Martin (Procne 

 purpurea) is very different from our Martins ; it is a 

 larger bird, as big as a Lark, glossy purple in the male, 

 the female being duller and white below ; it often builds 

 in boxes put up for it, as does the White-bellied Swallow 

 (Tachycineta bicolor), very like our House-Martin, but 

 with bare feet and no white patch on the back. In 

 India and Africa the Wire-tailed Swallow (Hirundo 

 smithii), blue-black above and white below, with chest- 

 nut cap and very long outer tail-feathers, is a well- 

 known bird locally. 



Tanagers {TanagrincB) are American, and chiefly 

 confined to the southern half of the New World. Their 

 bills are more or less conical in form, and exhibit the 

 nostrils exposed, but they vary in thickness of beak, 

 some species being almost indistinguishable from thick - 

 billed Finches, and others so slender in bill that they 

 grade into the American Warblers {MniotiltidcB). 

 These birds are chiefly fruit-eaters, build open nests, 

 and are often exceedingly brilliant and beautiful in 

 colour, the females being often almost equally so with 

 the males. Such is the case with the Brazilian Superb 

 Tanager (Calliste fastuosa), well known in captivity in 



