202 THE BIOLOGY OF BIRDS 



in the animal world. Darwin met the objection in various 

 ways. He pointed out that in some species the males out- 

 number the females, and that in some other species there is 

 polygamy. If the more attractive males have in such cases 

 an advantage in mating, the direction of evolutionary move- 

 ment will be determined by them, and not by the handi- 

 capped residue of the unattractive. He also pointed out 

 that the more vigorous and more attractive males would be 

 accepted by the more vigorous females which are the first 

 to breed, and this would imply a cumulative preponderance 

 of the more vigorous and more attractive types. Even 

 earlier hatching of the young birds might be of critical 

 moment. 



As a matter of fact, definite information as to the elimina- 

 tion of some of the males is by no means wholly lacking. 

 Thus in diagrammatic illustration w-e may refer to some 

 spiders where, as the Peckhams and others have shown, the 

 female sometimes kills a suitor who does not adequately 

 please her. That she may also kill a successful suitor is 

 immaterial, since the mating has been accomplished (see 

 G. W. and E. G. Peckham, " Observations on Sexual 

 Selection in Spiders of the family Attida?," Milwaukee, 

 1889, p. 60). 



As regards birds, Meisenheimer gives some good instances 

 in his important work on sex (1921, p. 766). A silver 

 pheasant that was for a while a prime favourite went literally 

 " off colour," and then a rival took his place. A captive 

 female of a weaver-bird {Sporceginthus ammidava) ahvays 

 gave the preference to the male with the most brilliant red, 

 and a female linnet in the same conditions always chose the 

 male with the brightest crimson on his breast. A similar 

 preference was clearly exhibited by one of the Tanagers 

 {Pyrafiga rubra) w^hich was the subject of experiment. It 

 seems to us that the reality of preferential mating has been 

 satisfactorily proved in certain cases. 



In the second place, many critics have objected to credit- 

 ing the female organism — whether bird or butterfly — with 

 the power of " choice," and while comparative psychology 



