SEASONAL CHANGE OF RELATIONSHIP 231 



Blackcap and a Lesser Whitethroat, or between 

 a Garden- Warbler and a Blackcap, but it is 

 of short duration and lacks vigour. Apart, 

 however, from such temporary disturbances, 

 there is no real rupture in their relations, and 

 certainly nothing to lead one to suppose that 

 the bickerings are determined by the functioning 

 of any~ specific instinct. Yet only a few months 

 previously some of them were constantly at 

 war, and their quarrels betrayed symptoms of 

 great persistence ; and if we remember how 

 the observed behaviour of the birds suggests 

 the fact that they were striving to attain some- 

 thing definite, we shall understand the nature 

 and exten.t of the change, and shall, I fancy, 

 be in a better position to estimate its biological 

 worth at its true value. 



We can find many similar examples — flocks 

 are to be found on arable ground, on the water 

 meadows, and on the mud-flats ; here different 

 kinds of Thritshes feed on the berries of the 

 yew, there different kinds of Tits travel together 

 in parties ; hosts of Finches collect in the hollies 

 to pass the night and Buntings roost together 

 in the gorse ; and, in fact, in whatever direction 

 we choose to look in the autumn and winter, 

 we find various birds assembled together and 

 living on amicable terms. All of this changes 

 in the spring, and the relationship undergoes 

 a gradual but noticeable alteration ; so much 

 so that whereas the outstanding feature of bird 

 life in the winter is sociability, that of the 

 spring is hostihty. 



Q2 



