EVOLUTION OF THE COLORS OF BIRDS. 259 



colors of the male of this form being sexual. Young 

 protectively colored. 



Genus Cyrtonyx. Massena Partridge. 



(7) Adult male more conspicuously colored than 

 female; young similar to adult female, but colors duller. 



Colors — Black, White, brown, rufous, buff, plumbe- 

 ous. 



The colors of the female are protective, of the male 

 for recognition. The Mexican forms, G. ocellatus and C. 

 sallcei, in which the flanks of the male are respectively 

 rich chestnut varied with black and plumbeous, and 

 " plumbeous, barred and spotted with chestnut," in dis- 

 tinction from G. montezutnce , which has no chestnut on 

 the flanks, are probably thus marked for sexual recogni- 

 tion, in distinguishing the three races. The pattern of 

 markings on the head of the male is one of the most 

 unusual and complex among North American birds, and 

 may very probably have originated at the time when 

 Cyrtonyx first separated from Callipepla. It was quite 

 likely a recognition mark exclusively at first, but may 

 have afterwards been accentuated and modified by 

 sexual selection from the mere attractiveness of some- 

 thing odd and grotesque, as Weismann has suggested in 

 commenting on tailless cats. (See ante, pp. 96-97.) ' 



Genus Dendragapas. The Grouse. 



(2) Male differing only slightly from female; young 

 with a peculiar first plumage. 



Colors — Black, white, slate-gray predominating — some 

 brownish, buffy, etc. 



An apparent tendency towards melanism by way of 

 cross barrings is present in this group. Retiring in its 

 habits, this genus has probably had little need for pro- 

 tection, and has in past times had few enemies as shown 

 by its " stolidity or indifference to the presence of man," 



