294 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



CHAETURA VAUXI (Townsend) 



VAUX'S SWIFT 



HABITS 



This, the smallest of the North American swifts, replaces in the 

 northwestern part of our continent the common chimney swift of the 

 eastern States. It breeds from southeastern Alaska and central Brit- 

 ish Columbia southward to the Santa Cruz Mountains of California 

 and eastward to Montana and Nevada; but it is rare east of the 

 Cascades and the Sierra Nevada. 



Throughout most of its range it is much less numerous than the 

 chimney swift is in the East. Most observers speak of it as rare dur- 

 ing the breeding season, but S. F. Rathbun tells me that in the vicinity 

 of Seattle, Wash., "the little Vaux's swift is more or less a common 

 bird. It arrives late in April and, though widely distributed, is more 

 apt to be seen in the river valleys, somewhat open, in which are tall, 

 dead trees; and quite likely one reason for this is that among such 

 trees are some that are hollow and will afford nesting places for the 

 birds." 



Spring. — ^While migrating, or when preparing to migrate, this little 

 swift often gathers into immense flocks. The following observation 

 by H. H. Sheldon (1922b), made at Santa Barbara, Calif., illustrates 

 this point: "On April 29, 1922, about 7 p. m., the largest flock of 

 Vaux Swift {Chaetura vauxi) I have ever seen or, in fact, heard of, 

 circled over my house several times. By careful estimate I judged 

 the number to be very nearly six hundred individuals. My observa- 

 tions of the Vaux Swift have heretofore been made only within its 

 breeding range ; while this is my first observation of a migrating flock, 

 such an immense gathering of this rather rare wilderness dweller is 

 no doubt a most unusual occurrence." 



Courtship. — Mr. Rathbun writes to me: "This swift does not ap- 

 pear to be mated when it comes, but after a short time some change 

 is noted in its actions. As they fly about, suddenly with a shrill 

 twitter one of the swifts makes a dash or a dive at another, and away 

 both rush, each striving to out-fly or out-dodge the other, the chase 

 brought to an end only when one escapes, or, as often is the case, both 

 fly off in company. As it appears to be quite playful, these actions 

 may be partly in sport, though at this particular time some must have 

 an earnest intent, for the courtship of this little swift evidently takes 

 place upon the wing." 



Nesting. — He says in his notes : "It begins to nest quite soon after 

 it has mated. Its nest is built inside a hollow tree, as in this respect 

 the bird chiefly follows the ancient habit of its kind. But with the 

 arrival of man changes have taken place in some of the primitive 



