Chap. IY. 
SEXUAL SELECTION. 
89 
believe that there is the severest rivalry between the 
males of many species to attract by singing the females. 
The rock-thrush of Guiana, birds of Paradise, and some 
others, congregate ; and successive males display their 
gorgeous plumage and perform strange antics before the 
females, which, standing by as spectators, at last choose 
the most attractive partner. Those who have closely 
attended to birds in confinement well know that they 
often take individual preferences and dislikes: thus 
Sir E. Heron has described how one pied peacock was 
eminently attractive to all his hen birds. It may 
appear childish to attribute any effect to such appa¬ 
rently weak means: I cannot here enter on the details 
necessary to support this view; but if man can in a short 
time give elegant carriage and beauty to his bantams, 
according to his standard of beauty, I can see no good 
reason to doubt that female birds, by selecting, during 
thousands of generations, the most melodious or beautiful 
males, according to their standard of beauty, might pro¬ 
duce a marked effect. I strongly suspect that some 
well-known laws, with respect to the plumage of male 
and female birds, in comparison with the plumage of the 
young, can be explained on the view of plumage having 
been chiefiy modified by sexual selection, acting when 
the birds have come to the breeding age or during the 
breeding season; the modifications thus produced being 
inherited at corresponding ages or seasons, either by 
the males alone, or by the males and females; but I 
have not space here to enter on this subject. 
Thus it is, as I believe, that when the males and 
females of any animal have the same general habits 
of life, but differ in structure, colour, or ornament, 
such differences have been mainly caused by sexual 
selection; that is, individual males have had, in suc¬ 
cessive generations, some slight advantage over other 
