146 RELATION OF SONG TO THE TERRITORY 



whereas the latter was only serviceable to 

 certain individuals ; and in making this state- 

 ment, I had in mind the direct benefits to the 

 community which proceeded from an apprecia- 

 tion of sounds having a mutually beneficial 

 meaning, not. the indirect, though none the less 

 beneficial, consequences to the species as a 

 whole. Biologically considered, song, if it acts 

 as a warning and thereby leads in one way or 

 another to more complete success in the rearing 

 of offspring, may be spoken of as socially 

 serviceable ; but it is legitimate to draw a 

 distinction between the prospective value of 

 remote relationships which we can foresee, 

 and the mutual assistance which the indivi- 

 duals of a community derive from their close 

 association. 



If there were always sufficient breeding 

 ground to support the offspring of all the 

 individuals of each species, if the individuals 

 were always so distributed that there was no 

 possibility of overcrowding in any particular 

 area, and if the conditions of existence of 

 different species were so widely divergent that 

 the presence of this one in no way affected the 

 interests of that, no opportunity would be 

 afforded for the development of so complex a 

 system as is involved in the " territory " and all 

 that appertains to it. But the available breed- 

 ing ground is by no means unlimited. The 

 supply of food, which is a determining factor 

 in the environment, is always fluctuating accord- 

 ing to the climate and according to the changes 



