38 BULLETIN 86, UNITED STATES NATIONAL MUSEUM. 



Argentina ; and Cordoba, north central Argentina ; south to Barracas 

 al Sud, Province of Buenos Aires, central eastern Argentina; and 

 east to Buenos Aires, central eastern Argentina ; Sao Paulo and Rio 

 de Janeiro, southeastern Brazil; and Guiana. Accidental north to 

 Melville Island, northern Canada. 



Remarks. — In the adult female of this race the posterior lower parts 

 are much more tinged with buff or ochraceous than in the male ; and 

 the ground color of the upper surface averages lighter, duller, and 

 more brownish, with more numerous light markings, which are more 

 buffy or ochraceous. 



Birds in first autumn plumage are, on the upper surface, almost 

 like the average of adult Chordeiles virginianus hssperis^ and similar 

 also to the adult of Chordeiles virginianus semiefti, but the dark 

 areas are more intensely blackish, though occasional specimens are 

 indistinguishable in this respect. 



The adult male is normally very deeply blackish above, with a 

 comparatively small amount of light mottling; but he varies individu- 

 ally to dull brownish, with a large amount of light marking, until 

 he becomes almost indistinguishable from dark examples of Chordeiles 

 virginianus howelli?- Light-colored specimens of this sort are No. 

 88139, U.S.N.M., Stamford, Connecticut, and No. 13249, E. A. and O. 

 Bangs, Santa Fe, Isle of Pines. The light markings of upper parts 

 are usually grayish, creamy white, and buff, but vary sometimes to 

 almost pure white, sometimes to deep tawny. The ground color of 

 the lower parts is normally grayish white, and varies little, though 

 sometimes almost pure white, sometimes slightly washed with buff. 

 The female is also variable above, and occasionally (such as No. 

 1T4915, U.S.N.M., Cumberland County, New Jersey; and No. 46920, 

 Mus. Comp. ZooL, Long Island, New York) very closely resembles 

 adult male Chordeiles virginianus hesperis. The ground color of the 

 ventral surface is commonly cream white, but deepens in some birds 

 to ochraceous buff. The light throat-patch is normally buff, ranging, 

 however, on the one hand to cream white, ou the other to deep ochra- 

 ceous buff. 



Notwithstanding its vast range, this subspecies exhibits almost no 

 geographical variation, except where its breeding area closely ap- 

 proaches that of some other race. Adult birds from Vancouver Island, 

 British Columbia, and from the Yukon River in Yukon are apparently 

 in no respect, of either size or color, distinguishable from those of 

 Nova Scotia, eastern Quebec, and New England. A single female 

 from Sproat's Landing, southeastern British Coulmbia (No. 970, 

 Victoria Mem. Mus., June 26, 1890), and another, a male, from 

 Banff, Alberta (No. 1256, Victoria Mem. Mus., June 8, 1891), both 

 seem to be typical of Chordeiles virginianus virginianus^ and appar- 



1 See p. 57. 



