GOATSUCKERS, HUMMING-BIRDS, ETC. 241 



nests are fastened to the perpendicular walls of old missions 

 or between crevices in the rocks. Occasionally an old, aban- 

 doned well is used. 



It is noticeable that swifts fly higher during clear, sun- 

 shiny weather, and an extreme or abrupt change in the 

 weather may be safely forecasted when the birds are noticed 

 skimming low over the roofs. 



Their only note is an unmusical twitter, which they utter 

 when flying at top speed. The shafts in the tail extend fully 

 one-quarter of an inch beyond the feathers, but these are not 

 visible in flying; neither is the insignificant bill; so that one 

 discerns merely a pair of long wings attached to a little 

 body, and the bird might easily be mistaken for a bat. 



Swifts are closely allied to nighthawks and the whip- 

 poor-wills. They exhibit little intelligence, except in the 

 construction of their nests, and, were it not for their abun- 

 dance in most sections, the birds would be little noticed by 

 the casual observer. Their flight, while strong and power- 

 ful, is not picturesque or graceful. The wing-beats are short 

 and rapid, but the bird sometimes soars when about to enter 

 a chimney. The outline against the sky reminds one of a 

 drawn bow and arrow. 



Accommodating itself to the aavance of civilization, the 

 nests are now usually placed on the inside of brick chimneys, 

 though they may be found firmly glued to the inside of a 

 barn or outbuilding. The nests are composed of small twigs 

 which the birds snap with beak from the trees while in flight. 

 These twigs are of about equal length, and are fastened to 

 each other by a glue in the form of saliva secreted by the 

 birds themselves from the throat. The nests are attached to 



