THE WHITE-THROATED SWIFT. 417 



an hour to flit from Spokane to Aberdeen; or, it might breakfast at Osooyoos 

 on tiie 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 sluily 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 rapidl}--filling jar of water. 



The birds exhibit a preternatural cunning in the selection of nesting 

 sites. Xot 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 affi.x 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 earlv 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 ever\' reason to suppose that other such colonies 

 e.xist in the Grand Coulee. 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 Dc Blois Green announces'' that 

 they have extended their range u]) the \alley of the Okanogan into British 



Columbia. 



• 



a. Life Hist. X. .\. Birds. \ol. 11., p. 185. 



b. .Mian Brooks in The .^uk. Vol. XX\I.. Jan. 1909. 



