*i 9 is J Hawkins, Sexual Selection and Bird Song. 435 



them an element of truth. If the purpose of song is excitation of 

 the female to break down her coyness, this very act may compel 

 her to exercise an unconscious choice and thus sexual selection may 

 exert a limiting and directive force in the life of the bird. Even 

 Hudson's theory that the bird sings out of the abundance of its 

 very being, joy and life, is not to be ignored. But the question 

 forces itself upon us, why does the bird sing and dance to overcome 

 the female coyness and what gives the male more vitality than the 

 female? The answers to these questions force us back into the 

 inner life of the bird to seek our answer in the essential difference 

 between the. sexes. 



So far as song, as well as other displays, in the mating season are 

 concerned they are due to the ripening of the sexual glands from 

 which, as Pycraft has shown, hormones "are set free, and, pervad- 

 ing the body, stimulate the nervous system, and at the same time 

 the secondary sexual characters — the antlers of the stag, the mam- 

 mary glands of the female, the 'breeding plumage' of the bird. 

 When they are obviously secondary sexual characters, as in the 

 case of dull colored birds, the result is the same, a state of physical 

 exaltation expressed in 'display.' Males or females wherein these 

 'hormones' are but feebly developed, display and respond in- 

 differently, and so cease to please the opposite sex. As Mr. 

 Howard has pointed out, in the ease of the Warblers, no amount 

 of display on the part of the male will avail until the female has 

 attained a like pitch of preparedness for the work of procreation. 

 The courtship of the ruffs and reeves, already referred to, afford 

 another illustration. Here it will be remembered the males for 

 weeks spend laborious days in endeavoring to gain some responsive 

 sign from their prospective but phlegmatic mates, yet without 

 receiving the slightest sign of encouragement or recognition. As 

 soon, however, as the female has become 'sexually ripe,' as soon 

 as the hormones secreted by her generative glands have done their 

 work, she herself indulges in a species of nuptial dance, waltzing 

 round her lord, and setting down before him with her tail directed 

 toward his head. Thus the sexual activity displayed by the male 

 comes to mean simply that he is more ardent at this time than his 

 mate. The advantage of this is obvious: for thereby the more 

 vigorous males, by proclaiming their desire to pair, defeat their 



