350 ANIMAL LIFE IX THE YOSEMITE 



piercing quality characteristic of the White-throated Swift. There was 

 much sailing along on set wings ; when the wings were flapped the beating 

 was sloAver than it is in either the White-throated or the Vaux Swift. 

 When the birds were at certain angles from the observer, striking flashes 

 of silvery gray were given off from the w^ings. 



Mr. Donald D. McLean believes that the Northern Black Swifts nest 

 in this vicinity in burned-out black oak stubs ; and he may be right. There 

 are no rock cliffs short of ten miles away; and he says the swifts have 

 been about the locality each summer ever since he can remember. He 

 occasionally sees one bird of a pair dart down from a great height, always 

 to disappear beyond some ridge or behind some large tree. He showed 

 one of us a prostrate hollow oak about which, before it fell, he says these 

 swifts used to be seen; but he never saw a bird actually enter a cavity. 

 With this hint, someone, sometime, with a stock of time, patience, and 

 favoring luck, may enjoy the thrill of the actual discovery of a Black 

 Swift's nest in the Yosemite region, 



W. 0. Emerson (1893, p. 179) recorded the Northern Black Swift as 

 "very common high up in all the cliffs, particularly [along] the face of 

 Glacier Point" in June, 1893. 



Vaux Swift. Chaetura vauxi (Townsend) 



Field characters. — Size about that of Violet-green Swallow; form and behavior like 

 those of White-throated Swift. Plumage plain blackish brown, except for silvery 

 suffusion on breast and throat. No white on flanks. 



Occurrence. — Noted in Yosemite Valley in fall (Mailliard, 1918, pp. 16, 18). Not 

 observed by us. Courses in open air, during day time. 



The Vaux Swift may be known in flight from the more common and 

 better known White-throated Swift by its smaller size, lesser degree of 

 whiteness on the throat, and by the absence of white on its flanks. It 

 is distinguished from the Northern Black Swift by its much smaller size 

 and by the silvery appearance of its throat and breast. 



This swift has been reported from Yosemite Valley by only one observer, 

 Mr. Joseph Mailliard (as above), who found it present in some numbers 

 in the early fall of 1917. "One or two often seen, and quite a flock at 

 times"; this statement referring to occurrence on August 21 and for a 

 few days subsequently (Mailliard, MS). 



Mr. Donald D. McLean reports the Vaux Swift as liaving occasionally 

 been seen by him in spring and summer at his lioine place 6 miles east 

 of Coulterville. 



