12 INTRODUCTION 



in reaching the breeding grounds, and, in 

 resident species, that they desert the females 

 and retire alone to their prospective territories, 

 so that there is a difference in the behaviour 

 of the sexes at the very commencement of 

 the sexual process. What is the immediate 

 consequence? Since the male isolates itself, 

 it follows, if the union of the sexes is to be 

 effected, that the discovery of a mate must 

 rest largely with the female. This of course 

 reverses the accepted course of procedure. 

 But after all, what reason is there to suppose 

 that the male seeks the female, or that a 

 mutual search takes place ; what reason to 

 think that this part of the process is subject 

 to no control except such as may be supplied 

 by the laws of chance ? 



Now, clearly, much will depend upon the 

 rapidity with which the female can discover a 

 male fit to breed ; for if the course of reproduc- 

 tion is to flow smoothly, there must be neither 

 undue delay nor waste of energy incurred in the 

 search — some guidance is therefore necessary, 

 some control in her external environment. 

 Here the song, or the mechanically produced 

 sound, comes into play, and assists in the attain- 

 ment of this end. Nevertheless if every male 

 were to make use of its powers whether it were 

 in occupation of a territory or not, if the 

 wandering individual had an equal chance of 

 attracting a mate, then it would be idle to 

 attempt to establish any relation between 

 "song" on the one hand, and "territory" on 



