66 BULLETIN 86, UNITED STATES NATIONAL MUSEUM. 



above, with the light mottlings coarser, more numerous, and much 

 more tawny ; below lighter, the dark areas of the anterior parts more 

 rufescent brown (less blackish) ; the light ground color of the posterior 

 surface decidedly more buffy, the dark bars narrower. From Chor- 

 deiles virginianiLs sennettl he may be distinguished by darker, much 

 more rufescent upper parts, with coarser and more tawny light 

 markings, and by the greater rufescence of the dark areas and the 

 more buffy suffusion of the light areas on the ventral surface. He 

 differs from Chordeiles mrginianus 'virgi7iianus in his much lighter, 

 more brownish (less blackish) ground color above, the light mottlings 

 being much more numerous, coarser, and more tawny; in the more 

 rufescent hue of the dark areas of lower surface, and generally 

 lighter tone below, the posterior parts more buffy, with narrower 

 dark brown bars. 



The female seems to be, on the upper surface, practically like the 

 male, but is decidedly more buffy on the posterior lower parts. She 

 may be distinguished from the female of Chordeiles mrginianus 

 hesperis by reason of her more rufescent (less grayish or blackish) 

 brown ground color above, with much coarser, more tawny light 

 markings. 



The Juvenal and first autumn plumages are much lighter on the 

 upper parts than are those of any of the other races excepting Chor- 

 deiles virgi7iianus sennettl and Chordeiles virginianus howelli. Com- 

 pared with the latter they are much more rufescent above, and, 

 because of this, somewhat darker. 



As in other races, there is a considerable range of individual varia- 

 tion in both size and color. The ground color of the posterior ventral 

 surface of the male is nearly always creamy or buffy white, but 

 occasionally varies to almost pure white. The same parts in the 

 female are buff or cream buff. The upper surface in both sexes is 

 normally dark rufescent brown, even somewhat blackish, with tawny 

 or tawny ochraceous mottlings. In some specimens, as, for instance, 

 in No. 20-151G, U.S.N.M., male, from the Hachita Mountains, New 

 Mexico, July IG, 1908, these light markings range to buff and even 

 whitish. Sometimes the ground color of the upper parts is of a much 

 lighter brown, so that it is much like that of Chordeiles mrginianus 

 howelli, as in No. G013, U.S.N.M., male, from Nogales, Arizona, June, 

 1857; and No. 16587, Field Museum, male, from the Huachuca 

 Mountains, June 7, 1901 ; but such specimens are distinguishable by 

 the more buffy abdomen. 



Breeding birds from southern Arizona and northern Chihuahua, 

 Mexico, represent the extreme differentiation of the present race. 

 Those from New Mexico are, as a whole, somewhat less ochraceous 

 or tawny, but are just as dark. A specimen from Taos, in northern 

 New Mexico, is intermediate between Chordeiles virginianus henryi 



