VAUX'S SWIFT 301 



wavered in the act, all seemed to have a single aim — to get inside the 

 chimney just as quickly as they could. 



"But this we noticed : that the temperature and the amount of light 

 prevailing each evening influenced the swifts as to the time they 

 would enter the chimney. On the cooler and darker ones the en- 

 trance would be made much earlier, whereas on the warmer and 

 fairer evenings they would enter it quite late." 



Dr. S. A. Watson (1933) made the following observation on an- 

 other method of roosting at Whittier, Calif., during the spring 

 migration : 



On the evening of May 12, 1933, large numbers of Vaux Swifts (Chactura 

 vauxi) were noticed circling around the barns of Mr. John Gregg near Whittier. 

 As night came on they began flying into a hay loft where they would cling to 

 the walls and to each other. At places they would cover large sections of 

 the wall five or six deep. It was estimated that at least three thousand swifts 

 found shelter in the barn that night. 



Next morning the birds began leaving the barn at about eight o'clock. They 

 would fly out, a few at a time, circle around a while and then fly ofE in groups. 

 They returned again the next two nights in about the same numbers, and for 

 the two nights following these the numbers decreased rapidly, and on the 

 sixth night they failed to return. The birds were heavily parasitized with 

 lice and seemed wealj and emaciated. A dozen or more were found dead each 

 morning during the period they were taking refuge in the barn. 



Since there was considerable snow in the mountains when the swifts were 

 staying over, it is assumed that the unfavorable weather barrier caused them 

 to accumulate here until warmer days and better feeding conditions called them 

 farther north. 



Voice. — ^Mr. Rathbun tells me that "its note is a rapid twitter, given 

 often as it dashes through the air with other swifts and sometimes 

 with the swallows, for it is a bird fond of company, though at times 

 only one or two are seen." Charles A. Allen (1880) says that the 

 note is different from that of the chimney swift : "They do not utter 

 the sharp, rattling chipper of that species, but have a weak, lisping 

 note, which is, as near as I can imitate it, chip-chip-chip-cheiueet- 

 cheweet, and this is only to be heard during the pairing season, when 

 two, probably the male and female, are chasing each other." Mr. 

 Hoffmann (1927) says: "On the breeding ground pairs of Vaux Swifts 

 pursue each other with a faint chip-chip-chipy 



Field marks. — ^Vaux's swift looks and acts like a small chimney 

 swift. It might be mistaken at a distance for the black swift, but 

 it is much smaller and much lighter in coloration below. It can 

 be easily distinguished from the white-throated swift, as it lacks the 

 conspicuous white areas on the breast and the flanks. Its flight, as 

 described above, is different from either of the other western swifts. 



Fall. — ^Mr. Rathbun's notes from the vicinity of Seattle, Wash., 

 containing the following observations on the migration through that 



