CYPSELID^ — THE SWIFTS. 427 



liundred feet high. It seemed to be very wary, and flew with great velocity, 

 rarely descending within reach of the guns. 



The White-throated Swift was met with in great abundance by Mr. Eidg- 

 way at the East Humboldt Mountains, and was seen by him more sparingly 

 in the Toyabe and Wahsatch. In tlie former mountains it inhabited tlie high 

 limestone clift's which walled the caflons, congregating in thousands, and 

 nesting in the chinks or crevices of the rocks, in company with the Violet- 

 green Swallow {Tachycinda thalassina). It was a very noisy species, having 

 a vigorous chatter, reminding one somewhat of the notes of young Baltimore 

 Orioles when being fed by their parents. It was also very pugnacious, a 

 couple now and then being seen to fasten upon one another high up in the 

 air, and, clinging together, falling, whirling round and round in their descent, 

 nearly to the ground, when they would let go each other, and separate. 

 A couple would often rush by with almost inconceivable velocity, one in 

 chase of the other. Their flight was usually very high, or, if they occasion- 

 ally descended, it was so swiftly that Mr. Eidgway only succeeded in shoot- 

 ing three specimens, while he found it utterly impossible to reach their nests, 

 which were in the horizontal fissures in the face of the overhanoino- cliff. 



Subfamily CH^TURIN.ffi. 



This subfamily is characterized by having the normal number of phalanges 

 to the middle and outer toes (4 and 5, instead of 3 and 3), the backward 

 position of the hind toe, and the naked tarsi, which do not even appear to 

 be scutellate, but covered with a soft skin. Of the two North American 

 genera, Ghcetura has spinous projections at the end of . the tail-feathers, 

 while in Nephcecetes the shafts of the tail-feathers, though stiffened, do not 

 project beyond the plume. 



This subfamily appears to be composed of two definable sections, with 

 subdivisions as follows : — 



A. Tail forked ; spinous points of the feathers not extending far beyond the 

 webs, or entirely wanting. Feathering of the sides of the forehead extending 

 forward outside the nostrils nearly to their anterior end. 



a. No trace of spinous points to tail-feathers. Feathering of frontal points 

 almost completely enclosing the nostrils between them. No light collar 

 round the neck ; sides of the forehead with a hoary suffusion . . Nephcecetes. 

 h. Spinous points of tail-feathers distinct. A light collar round the neck. 



1. Nostril as in Neplioicetes. Sides of forehead with a hoary suffusion. 

 Collar chestnut. Wing less than 5.50. ( C. rutila.) 



2. Feathered frontal points narrower, not reaching anterior end of 

 nostril. Sides of forehead without hoary suffusion. Collar white. 



Wing more than 8.00 ........ Hemiprocne. 



B. Tail rounded ; spinous points of the feathers much elongated and projecting. 

 Feathering of sides of forehead scarcely reaching beyond posterior end of nostril. 



Wing less than 5.50 Chcetura. 



