PURPOSE OF SONG 153 



Spasmodic outbursts of this kind, stimulated 

 by an isolated utterance, are by no means 

 uncommon. But not only does song stimulate 

 song ; under certain conditions it has the still 

 more remarkable effect of arousing hostility. 

 The boundary that separates two adjoining 

 territories is by no means a definite line, but 

 rather a fluid area wandered over by this 

 owner at one moment, by that at another. 

 Now so long as the bird is silent while in this 

 area, the probability is that it will escape 

 detection and remain unmolested ; let it however 

 sing— it often does so — and it will not merely 

 be approached but attacked, and consequently 

 this area is the scene of much strife. The point 

 to be noticed here is that the song brings about 

 no withdrawal ; it elicits a response, attracts 

 instead of repelling, and, in short, arouses the 

 impulse that is always predominant in the 

 nature of the male when eventually it occupies 

 a territory — the impulse of self-assertiveness. 

 Therefore it seems clear that the diiFerent stages 

 in the process of reproduction mark the appear- 

 ance of different conditions, each of which 

 renders some new impulse susceptible to 

 stimulation, and that the significance of song 

 depends upon the stage which happens to 

 have been reached. Hence when we speak 

 of song acting as a "warning," we do not 

 mean that it arouses any sensation of fear; it 

 is but a stimulus to that part of the inherited 

 nature of the hearer which predominates at the 

 moment. 



