THE GENUS CHORDEILES SWAINSON — OBERHOLSER. 29 



peris^ the Pacific coast race, which extends also eastward over the 

 arid Great Basin. The four southeastemmost forms, Chordeiles 

 virginianus aserriensis, Chordeiles virginianus chapmani^ Chordeiles 

 virginianus vicinus, and Chordeiles virginianus minor are the small- 

 est, and of these the two island races, C. v. vicinus and C. v. minor, 

 represent the minimum. The five remaining races are all of large 

 size and practically alike in this respect. It is interesting to note 

 the reduplication of certain characters, such as the coloration of the 

 upper parts, in forms widely separated geographically. Thus 

 Chordeiles virginianus vicinus, except for its small size and more 

 ochraceous lower surface, would pass very well for the far distant 

 Chordeiles virginianus hesperis of Oregon and California; while 

 Chordeiles virginianus m,inor of Cuba bears similar resemblance to 

 Chordeiles virginianus henryi of Arizona. Furthermore, it is doubt- 

 less worth while to mention the development of blackish or dark 

 grayish races in the northern and eastern portions of North America ; 

 of a light grayish form on the northern Great Plains ; of light, rather 

 ochraceous races in the middle Rocky Mountains, the southern part of 

 the Great Plains, and in Texas; of a rather dark, very tawny or 

 ochraceous subspecies in arid Arizona and New Mexico; and of a 

 dark, very tawny or ochraceous but very small bird on the Greater 

 Antilles. 



The nine forms of Chordeiles virginiam/m here recognized are com- 

 monly considered subspecies, and correctly so. The Cuban Chor- 

 deiles virginianus minor indicates by the range of its individual vari- 

 ation its close connection with Chordeiles virginianus vicinus of the 

 Bahama Islands, which race in turn overlaps in the same way the 

 characters of Chordeiles virginianus chapmani. The last mentioned 

 passes gradually through geographical intermediates into Chordeiles 

 virginianus virginianus. In the same manner Chordeiles virginianus 

 virginianus intergrades with Chordeiles virginianus sennetti and 

 Chordeiles virginianus hesperis^ and the last with both Chordeiles 

 virginianus sennetti and Chordeiles virginianus howelli.^ Chor- 

 deiles virginianus howelli^ intergrades geographically with Chor- 

 deiles virginianus henryi, and both of these with Chordeiles virgini- 

 anus aserriensis, which in turn connects with Chordeiles virginianus 

 chapmani. 



Most of the characters distinguishing the subspecies of Chordeiles 

 virginianus lie in differences of size, chiefly of wing and tail, some- 

 times also of tarsus and middle toe ; of the general tone of the upper 

 surface, whether light or dark, grayish, blackish, buffy, ochraceous 

 or tawny, this lightness or darkness due to the difference in ground 

 color and in the color, abundance, and fineness of the light markings ; 

 of the general tone of the lower surface, whether light or dark, 



1 See p. 57. 



