316 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



flight of this swift is often more or less direct, but it darts and swoops, 

 and turns so quickly as it flies that the eye is not quick enough to see 

 how the reversal in the direction of its flight takes place. You watch 

 one as it passes, almost disappears, and in an instant it returns and 

 flashes by. Its flight is so unpredictable that one never knows what 

 next it will do. At rare times, we have seen the white-throated and 

 the black swift in company, and this gave us an opportunity to com- 

 pare the flight actions of the two. Always the flight of the former 

 is dashing, whereas that of the latter is easy and graceful, as it glides 

 around." 

 Mr. Hanna (1917) writes: 



It is claimed by some that these birds do not use their wings in unison, but 

 I am of the opinion that they do flap both wings at the same time, at least 

 part of the time if not always. When flying about feeding upon insects, usually 

 at several hundred feet elevation above the ground, they make a few rapid beats 

 with the wings, then soar a little while, then beat their wings rapidly for a few 

 moments and so on. They vary their flight by sharp darts in other directions, 

 probably to catch insects. When returning to the cliffs they often keep their 

 wings beating fairly steadily. Both when penetrating and leaving the crevices 

 they seem to use both their wings and feet as aids to locomotion. * * * 



During the heavy rains of January, 1916, quite a number of swifts were found 

 on the ground in a helpless condition. It seems that some of the crevices had 

 become flooded with water which had drenched the birds, causing them to attempt 

 to escape, but it was impossible for them to fly with wet feathers. Several of 

 these birds were kept in a warm place till their feathers were dry enough for 

 them to fly away. 



The white-throated swift has well been called the rock swift, for it 

 lives its life in the rocky cliffs and in the air. So far as I know, no 

 one has ever seen one alight on the ground, on a tree, or on any kind 

 of perch. Its feet are not well formed for walking or perching, but 

 they are well adapted, with long, strong claws, for climbing about in 

 the caves and crevices in the cliffs. Mr. Dixon says in his notes: 

 "Their legs are so malformed from nonuse as to be almost nothing 

 but claws, to propel them through the cracks; and they can climb 

 around much the same as bats or mice in such a location." 



The photograph and the diagram published by Enid Michael 

 (1926) illustrate this character. 



Dr. Gayle Pickwell (1937) gives an interesting account of the 

 roosting habits of this swift in Santa Clara County, Calif. : 



The niche in which the swifts quartered themselves in 1931, and throughout 

 the observations here reported upon, consists of a recess of unknown depth 

 extending beneath a rock face that lies at an angle a little short of the vertical. 

 It is about fifteen feet immediately above Sycamore Canyon Road. The crevice 

 through which the swifts enter and leave measures, it is estimated, from two 

 to three inches in width and about two and one-half feet in length. All the 

 swifts noted, during the dates specified, used this aperture and this one only. 



