THE INFLUENCE OF COMBAT 35 



" In some of these cases the habit of singing may be 

 in part attributed to the female having been highly 

 fed and confined, for this seems to disturb all the 

 usual functions connected with the reproduction of the 

 species. ... It has been also argued that the song 

 of the male cannot serve as a charm, because the 

 males of certain species, for instance of the robin, 

 sing during autumn. But nothing is more common 

 than for animals to take pleasure in practising what- 

 ever instinct they follow at other times for some real 

 good" (Descent of Man, p. 369). Singing affords 

 almost the only means of occupying the ample 

 leisure of a captive bird. 



Amongst polygamous species the selection of 

 mates is largely dependent upon victory in combat ; 

 and this may account not only for the defiant 

 nature of the cries of male Gallinaceous birds, but 

 also for their lack of varied song. The males 

 capture rather than woo their mates : hence sweet- 

 ness of voice is of far less advantage than strength 

 and fury in their courtship. 



It is clear that a widely -prevalent snapping 

 noise made with the bill has been developed among 

 birds as a menace ; and it corresponds to the 

 display of teeth by an angry dog, and the waving 

 of the horns and lowering of the head of an 



