SUMMARY 257 



some control over the local distribution of 

 species is of paramount importance. Neverthe- 

 less, if all the different forms that require similar 

 conditions of existence were intolerant of one 

 another in a like degree, the smaller bird would 

 have no chance in competition with the larger. 

 This, however, is not the case. Some, as we 

 saw, arouse little or no animosity in others, in 

 fact the more closely related the rivals, the more 

 responsive their pugnacious nature seems to 

 become. 



To return now to the view that the fighting 

 is not really serious, but, on the contrary, that it 

 is either vestigial and has no longer any part to 

 play in furthering the life of the individual, or 

 that it is a by-product of the seasonal sexual 

 condition to which no meaning can be attached. 

 First, there is the relationship with the territory, 

 and this, it seems to me, is a fact of some 

 importance ; for if the fighting were merely an 

 exuberant manifestation of sexual emotion, one 

 would expect to find it occurring under all 

 conditions, and not merely under one particular 

 condition in the life of the bird. The hostility 

 is too widespread, however, and too uniform in 

 occurrence for us to suppose that it has no root 

 in the inherited constitution of the bird ; and if 

 it served some useful purpose in the past, the 

 instinct might still persist, so long as it were not 

 harmful. Thus the view that the behaviour is 

 vestigial is not perhaps unreasonable. But 

 manifestly it makes no difference whether it be 

 vestigial or a by-product of sexual emotion. 



