INNATE ABILITY 281 



a ceaseless energy directed towards a definite 

 end which for us, who can perceive its prospective 

 value, is isolation in an appropriate environment. 

 The emphasis here is on "isolation," for it 

 involves competition, and there cannot be com- 

 petition without some change in the relative 

 positions occupied by different individuals ; so 

 that in each recurring season there will be 

 not only a re-arrangement of ground formerly 

 occupied but an arrangement of ground formerly 

 deserted. 



(2) That the older birds return to the 

 locality wherein they had formerly reared 

 offspring, and the younger to the neighbour- 

 hood of their birthplace, was always deemed 

 probable. But in recent years evidence which 

 cannot be rebutted has been supplied by the 

 marking of birds. This evidence, details of 

 which can be found in the summary of results 

 published annually by Mr Witherby in British 

 Birds, demonstrates that the adult frequently 

 returns not only to the same locality in which 

 it formerly bred, but even to the same station ; 

 that it does so year after year ; that this mode 

 of behaviour is not peculiar to one sex ; and 

 that many of the young breed in the locality 

 in which they were reared. Such being well- 

 established facts, we can infer the existence of 

 an innate ability to revisit the place wherein 

 the enjoyment of breeding, or of birth, had 

 formerly been experienced. Of its nature we 

 know little or nothing. It would almost seem 

 as if there must be some recollection of past 



