EVOLUTION OF THE COLORS OF BIRDS. 267 



barrings on the tail, probably in accordance with the 

 principle of repetitive marks rather than for any prin- 

 ciple of utility, have in many species extended up on 

 the body, especially upon the flanks, but in some in- 

 stances over the back as well. 



FAMILY CATHAETID^. The American Vultures. 



(1) Male like female (except for the fleshy comb on 

 the cere); young but little different from adult. 



Prevailing colors, black, dark brown, white. 



In the three North American genera, Pseudogryphus, 

 Cathartes and Catharista, the colors are of no utilitarian 

 significance whatever, except that a black bird may be 

 seen at a great distance in the sky, and they might thus 

 assist one another in congregating at a place where food 

 had been discovered. Natural selection would thus en- 

 courage this general tendency towards the assumption of 

 a melanistic plumage. 



FAMILY FALCONIDiE. Vultures, Falcons, Hawks, 

 Eagles, etc. 



Genera Elanoides, Elanus, Ictinia and Rostrha- 

 Mus. The Kites. 



(2) Male like female; young with peculiar first plu- 

 mage. » 



Prevailing colors, black, white, plumbeous, bluish 

 gray, brown (in young). 



It is not easy to see how the beautiful uniform white 

 and bluish gray marks, relieved by patches of black in 

 the kites, can be of any more utility than a similar style 

 of plumage is among the gulls. In both instances the 

 colors may be in general, of use for recognition, although 

 such pleasing tints would hardly be necessary for this 

 purpose. There is a great temptation in this instance 



