426 NORTH AMERICAN BIRDS. 



the crevices of rocks, and that their eggs are pure white, and of an elongated 

 form. 



Dr. Coues found this species rather sparingly distributed throughout Ari- 

 zona, always in the neighborhood of cliffs and precipices, which it exclu- 

 sively inhabits. From Inscription Eock, about one day's march from 

 Whipple's Pass, to the San Francisco Mountains of Arizona, he found these 

 birds in great numbers, except along the valley of the Colorado Chiquito, 

 where there were no suitable cliffs for their habitation. He generally found 

 them congregated in considerable, sometimes in immense, numbers in the 

 vicinity of huge cliffs and piles of rocks. Their note, he adds, is an often and 

 quickly repeated twitter, loud and shrill, and quite different from that of 

 the C. ^dagica. He states that they build their nest upon the vertical faces 

 of precipitous rocks. 



Dr. Woodhouse met with a Swift in the same region referred to by Dr. 

 Coues, which he called Acanthylis saxatilis, which may possibly be the same 

 species, but of which no specimen was procured. They were breeding in 

 the crevices of the rocks. The description, however, does not at all corre- 

 spond. 



This species has lately been met with by Mr. Salvin, in Guatemala, where 

 it is by no means common, and so very local that its presence might readily 

 have been overlooked. He found it near Duehas, in a gorge with precipi- 

 tous rocks on the right hand, along the course of the river Guacalate. His 

 attention was drawn to a noise coming from the rocks, which he at first took 

 to be bats in some of the cracks. After watching for some time, he saw two 

 Swifts dart into a crack in the rock twenty feet from the ground, and the 

 noise became louder than before. Eesorting to several expedients, in vain, 

 to make them fly out, he climbed up part way, and there found one of them 

 killed by a random shot of his gun. Another discharge of his gun brought 

 out five or six more, which were immediately pursued by the Cotyh serri- 

 pennis. He obtained three specimens in all. The spot was evidently their 

 common roosting-place, and by the noise they made he judged they were 

 there in large numbers. He found them about the middle of February. 



Dr. Cooper met with this species near Fort Mohave, but saw none before 

 May. On the 7th of June, near tlie head of Mohave Eiver, he found a few 

 about some lofty granite cliffs, and succeeded in obtaining one. Their flight 

 was exceedingly swift and changeable, and they were very difficult to shoot. 

 He also found them about some high rocky bluffs close to the sea-shore, 

 twelve miles north of San Diego. They were seen the last of March, but 

 may have been there for a month previously. 



Mr. Allen encountered tliis little-known Swift near Colorado City, where 

 it was qu.ite numerous about the high cliffs in tlie " Garden of the Gods," 

 and of which, with great difficulty, he procured four specimens. It was 

 nesting in inaccessible crevices and weather-beaten holes in the rocks, about 

 midway up the high vertical cliffs, some of which were not less than three 



