EVOLUTION OF THE COLORS OF BIRDS. 87 



has argued, but the choice is really made by the female. 

 Mr. Wallace has, however, interposed another objec- 

 tion of great importance. He says: * " Again, evidence 

 collected by Mr. Darwin himself, proves that each bird 

 finds a mate under any circumstances. He gives a num- 

 ber of cases of one of a pair of birds being shot, and the 

 survivor being always found paired again almost im- 

 mediately. This is sufficiently explained on the assump- 

 tion that the destruction of birds by various causes is 

 continually leaving widows and widowers in nearly equal 

 proportions, and thus each one finds a fresh mate; and 

 it leads to the conclusion that permanently unpaired 

 birds are very scarce, so that, speaking broadly, every 

 bird finds a mate and breeds. But this would almost or 

 quite neutralize any effect of sexual selection of color 

 or ornament, since the less highly-colored birds would 

 be at little or no disadvantage as regards leaving healthy 

 offspring." If it were indeed true that every male bird 

 found a mate there would be a serious difficulty in the 

 way of sexual selection, but Mr. Wallace has not estab- 

 lished this in the passage above quoted. It seems quite 

 as natural to suppose that there are always a number of 

 birds who have not found mates, and that consequently 

 there are constantly a supply of bachelors and old maids 

 on hand to mate with any unfortunate widow or widower. 

 Collectors of birds have often commented on the fact 

 that several males are nearly always shot to one female. 

 To be sure the duller colors and m.ore retiring habits of 

 female birds would insure their protection, but even 

 where special search is made for them they are found to 

 be less common than the other sex. This is noted, 

 moreover, among species in which the sexes are alike. 

 If there be such a preponderance of males as seems 



'I. c, p. 370. 



