CHAPTER VIl 



THE KELATION OF THE TERRITORY TO 

 MIGRATION 



Coincident in' time with the growth of 

 appropriate conditions in the environment, 

 organic changes take place rendering certain 

 instincts susceptible to stimulation ; and the 

 stimulus being applied, the Warbler leaves the 

 country wherein it had passed the winter and 

 finds its way back, with apparently little 

 difficulty, to the district in which it was reared 

 or had previously reared oflfspring. What is 

 the nature of these changes and of the impulse 

 which is first brought into functional activity ; 

 whence comes the stimulus ; and what directs 

 the bird on its journey — these are all different 

 aspects of one great problem, the problem of 

 migration. I do not propose to discuss all these 

 various aspects, for indeed I have no suggestions 

 to offer which are in the least likely to be 

 helpful, but I seek rather to ascertain whether 

 the phenomena which we have explored bear 

 any relation to the problem "^as a whole ; 

 whether, that is to say, the competition for 

 territory and all that appertains to it can have 



