274 RELATION OF TERRITORY TO MIGRATION 



outskirts of the territory it was invading, and 

 used them as a base from which it made 

 repeated efforts to enter the ground of its rival. 

 These efforts were time after time frustrated. 

 No sooner did it leave its base than it was seen 

 and intercepted, or else attacked ; and no matter 

 from which direction it attempted to effect an 

 entrance, its efforts, for a time, were all to no 

 purpose. The fighting was of a determined 

 character, and after each attack the owner of 

 the territory showed signs of great excitement, 

 and, sitting upright upon a branch, spread and 

 waved its wings, which is the specific emotional 

 manifestation during the period of sexual 

 activity. Eventually the intruding male suc- 

 ceeded by persistent effort in appropriating part 

 of the occupied ground. 



Thus we can actually witness the efforts of 

 the individual to isolate itself from members of 

 its own kind, and can observe the immediate 

 consequences that follow from success or from 

 failure. And from these consequences we can 

 infer that, within a certain range but in accord- 

 ance with the relative abundance of the species 

 that dwell in it, every corner of the available 

 breeding ground will be explored and every 

 situation that evokes the appropriate response 

 will be occupied. Moreover, since the annual 

 dispersion is not merely a repetition in this 

 season of that which o_ccurred in a previous one, 

 a progressive increase in the area occupied will 

 follow. Yet, if the majority of species desert 

 their breeding ground so soon as reproduction is 



