THE WHITE-THROATED SWIFT. __ 417 
an hour to flit from Spokane to Aberdeen; or, it might breakfast at Osooyoos 
on the Forty-ninth Parallel, lunch in Chihuahua, and dine, a trifle late, in 
Panama. 
This Rock Swift nests only in crevices and caves of the most inaccessible 
cliffs. Most of its hunting, however, is done in the upper air, where its 
lighter colors soon render it indistinguishable. It appears also to be less 
sociable than the other species upon the hunt, so that almost the only op- 
portunities for careful study of it are afforded near the cliffs. Here there 
is much amorous pursuit, and the frequent sound of thrilling notes. The 
characteristic notes constitute a sort of war-cry, rather than song, and con- 
sist of a liquid descending scale of musical chuckling, or rubbing tones. 
The noise produced is much as if two pebbles were being fiercely rubbed 
together in a rapidly-filling jar of water. 
The birds exhibit a preternatural cunning in the selection of nesting 
sites. Not only do they choose sheer walls, but those which, because of the 
fissures so afforded, are crumbling and dangerous to a degree. The butte 
shown in the illustration consists of a hard lava capping over a disintegrating 
bed of tufa, impossible of ascent and impracticable of descent. Here in some 
remotest crevice the birds affix a narrow shelf, of straws, bits of weed- 
stalks, and miscellaneous trash, agglutinated with saliva; and in this four or 
five narrowly elliptical white eggs are deposited late in June or early in 
July. 
These interesting birds are newcomers within our borders, and their 
comings and goings are as yet little known. Bendire in 1895 remarked? 
their utter absence from Oregon and Washington. In 1896 I saw a single 
bird in the gorge of the Columbia near Chelan, and upon revisiting this 
scene in May, 1906, found that quite a colony of them were haunting a 
granite wall some 800 feet in height. Late in the same season, and in each 
succeeding year I have found them in the vicinity of Cold Spring Butte in 
Douglas County; and have every reason to suppose that other such colonies 
exist in the Grand Couleé. In the summer of 1906 Mr. Bowles and myself 
observed them crossing the Cascade Pass in company with Black Swifts; 
while still more recently, Mr. Charles De Blois Green announces? that 
they have extended their range up the valley of the Okanogan into British 
Columbia. 
a. Life Hist. N. A. Birds, Vol. II., p. 185. 
b. Allan Brooks in The Auk, Vol. XXVI., Jan. 1909. 
