EVOLUTION OF THE COLORS OP BIRDS. 277 



It is difficult to find any use for the general markings 

 of this group, but with what is known of the remark- 

 able tendency toward protective mimicry of the cuckoos 

 in all parts of the world, it is not impossible that the 

 plumage of this genus may be an imitation of the mark- 

 ings of some extinct species of hawk, some form allied 

 to Accipiter velox, for instance. However this may be, 

 the differences between G. americana and C. erythroph- 

 thalmus are doubtless discriminative in nature, the 

 yellow bill and distinct white spots on the tail of the 

 former serving to distinguish it very readily from the 

 latter. C. minor and G. maynardi have been differen- 

 tiated by isolation upon groups of islands, the direct 

 influence in the environment perhaps aiding in the 

 changes of their plumage. 



FAMILY TROGONID.E. The Trogons. 



Genus Trogon. The Trogons. 



(8) Male more conspicuously colored than female; 

 young with a peculiar first plumage. 



Prevailing colors, metallic green, black, red, yellow, 

 gray, white. 



This tropical genus is represented by but one species 

 along our southern border, and the colors may be ac- 

 counted for by the action of sexual selection, together 

 with a tropical climate. The areas of color are the same 

 in the female as in the male, but the bright metallic 

 shades are replaced by brownish or grayish. The 

 plumage of the young is still less specialized than that 

 of the female, the species thus exhibiting three stages 

 of evolutionary progression. 



