462 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



same time vigorous males, they will rear a larger number of offspring 

 than the retarded females which must pair with the less vigorous and 

 less attractive males. So it will be if the more vigorous males select 

 the more attractive, and at the same time healthy and vigorous 

 females; and this will especially hold good if the male defends the 

 female and aids in providing food for the young. The advantage 

 thus gained by the more vigorous pair in rearing a larger number of 

 offspring, has apparently sufficed to render sexual selection efficient.*' 



Wallace was the first critic of the sexual selection theory. He 

 admits the display of gorgeous colors, the antics and songs of 

 the male bird before the female, as fully demonstrated by Darwin, 

 but he says, " it by no means follows that slight difference in the 

 shape, pattern, or colors of the ornamental plumes are what lead a 

 female to give the preference to one male over another; still less that 

 all the females of a species, or the great majority of them, over a 

 wide area of country or for many successive generations prefer 

 exactly the same modifications of colors or ornament." Thus he 

 rules out the idea that the female makes a conscious choice of the 

 male most highly colored or who is the best singer. But this does 

 not destroy the idea that there may be an unconscious choice. Indeed, 

 Wallace seems to admit this possibility when he says, "As all the 

 evidence goes to show that, so far as female birds exercise any choice, 

 it is of the most ' vigorous, defiant, and mettlesome ' males, this form 

 of sexual selection will act in the same direction (as natural selec- 

 tion), and help to carry on the process of plume development to its 

 culmination." If this choice exercised by the female is unconscious 

 rather than conscious, Darwin's theory is not vitally affected. All he 

 is anxious to demonstrate is that the most vigorous bird succeeds in 

 winning the most desirable mate, however the choice may be made, 

 and if he succeeds in this the bird may pass to his offspring his own 

 characters which in succeeding generations will become permanent. 



But Wallace goes deeper in his criticism than the mere matter of 

 choice. He attributes the origin of song to natural selection rather 

 than to sexual selection. Darwin begins with sober colors and 

 attributes the gay colors of the males to selection on the part of the 

 female. Wallace starts with the gorgeous colors and declares that 

 the gray colors of the females are due to natural selection. Bright 

 plumage would render the mother bird sitting on her nest con- 

 spicuous and make her the easy prey to hawks and other natural 

 enemies. Hence all the highly colored females, through generations, 

 have been destroyed, only the more sober colored birds remaining. 



The original brightness has been forfeited by the sex as a ransom for life. 

 Female birds in open nests are similarly colored like their surroundings ; while 

 in those birds where the nests are domed or covered, the plumage is gay in both 

 sexes. 



