454 FAMILY HIRUNDINID.K; SWIFTS. 



408. The Swift has probably the most imperfect feet of any 

 known bird. Owing to their extreme shortness, it is unable to 

 walk, except with a most constrained and hobbling gait, and 

 with the assistance of the wings ; and from the same cause, in 

 combination with the extreme length of the wings, the bird 

 cannot rise from a flat horizontal surface, since its body is not 

 sufficiently elevated above it to admit of the first downward 

 stroke of these members (333). The Swift, consequently, never 

 settles on' the ground ; but alights only in such places as present 

 a brink, or declivity, from the edge of which it can launch itself. 

 The toes are furnished with strong claws ; the direction of which 

 is such, that the bird can cling very securely even to a perpen- 

 dicular surface. It lives habitually, and pursues its prey, at a 

 greater height from the ground than the Swallows ; and it con- 



FIG. 255. HEAD OK BLACK SWIFT. 



structs its nest at a more lofty elevation, choosing the crevices of 

 steeples and towers, and the crannies of rocks. 

 The nest is composed of twigs, straws, and 

 feathers, carefully arranged, but cemented 

 together by glutinous matter. The height 

 at which the Swifts fly, a good deal depends 

 FOOT OF BLACK SWIFT. on the state of the wea ther. When the 



atmosphere is pure and dry, their flight is most elevated ; 

 for it is then that their insect prey rise highest on the wing. 

 When it is moist, on the other hand, they fly much lower ; 

 and sometimes come down so far, as almost to touch the sur- 

 face of the water over which they skim. The amount of their 



