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 Arizona, always in the neighborhood of cliffs and precipices, which it exclusively inhabits. From Inscription Rock, 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. pelagica. 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 correspond.
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 Dueñas, in a gorge with precipitous 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. Resorting 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 Cotyle serripennis. 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 the head of Mohave River, 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 this little-known Swift near Colorado City, where it was quite numerous about the high cliffs in the “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
hundred 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. Ridgway at the East Humboldt Mountains, and was seen by him more sparingly in the Toyabe and Wahsatch. In the former mountains it inhabited the high limestone cliffs which walled the cañons, congregating in thousands, and nesting in the chinks or crevices of the rocks, in company with the Violet-green Swallow (Tachycincta 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 occasionally descended, it was so swiftly that Mr. Ridgway only succeeded in shooting three specimens, while he found it utterly impossible to reach their nests, which were in the horizontal fissures in the face of the overhanging cliff.
Subfamily CHÆTURINÆ.
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, Chætura has spinous projections at the end of the tail-feathers, while in Nephœcetes the shafts of the tail-feathers, though stiffened, do not project beyond the plume.