COURTSHIP AMONG BIRDS 93 



an aspect of the subject which has a far more important 

 bearing on the problems of evolution than is generally 

 realized. But these pages are concerned rather with the 

 relations between the sexes, than with the subtle forces 

 which have fashioned and control conduct in this regard. 



In all that concerns the problems of sex, which is to 

 say of reproduction, birds, speaking generally, display 

 a briefer and more condensed sequence of events than 

 the mammals ; and, moreover, many species compel the 

 attention even of the most incurious, to their behaviour 

 at this time, through the development, either of song, or 

 of fantastic displays of their amorous feelings : while others 

 force themselves no less conspicuously under notice by 

 their habit of nesting in large, and often enormous colonies. 



In the matter of the development of secondary sexual 

 characters birds stand conspicuous among the Vertebrates, 

 and easily eclipse the mammals; among which bright, 

 strongly contrasted, colours are the exception. Among 

 the birds they may almost be said to be the rule. Also, 

 in this category we have to reckon song, and the pro- 

 duction of more or less musical sounds by the agency of 

 internal resonators or of specially modified feathers ; 

 as well as quaint forms of posturing which may be 

 included under the head of dances. Further, some species 

 have developed formidable weapons of offence. These 

 things are interesting enough in themselves, but they 

 become still more so when we reflect that they formed 

 the corner-stone of Darwin's theory of " Sexual Selection," 

 and that Wallace's criticisms thereof were inspired by 

 evidence from the same source. 



The interests of this chapter will best be served if the 

 evidence on which this theory was founded be first sur- 

 veyed : when Darwin's deductions and the criticism 



