EFFECT OF EXPOSURE ON THE YOUNG 187 



must be, in the vicinity of the nest, an adequate 

 supply of food upon which the parents can draw 

 liberally. Hence those pairs that exercise 

 dominion over the few acres surrounding the 

 nest, and are thus able to obtain food rapidly, 

 will stand a better chance of rearing their 

 oiFspring than others which have no certain 

 supply to draw upon — and this, I believe, is one 

 of the biological ends for which the territory has 

 been evolved. But it must not be supposed 

 that each pair finds, or even attempts to find, 

 the whole of the food within its territory, or 

 that it is necessary for the theory that it should 

 do so ; all that is required is that such over- 

 crowding as might lead to prolonged absence on 

 the part of the parents and inordinate exposure 

 of the young shall be avoided. So that the 

 problem has to be considered not merely from 

 the point of view of the individual, but from the 

 larger point of view of all the pairs inhabiting 

 a given area. 



Now there were eight pairs of Yellow 

 Buntings occupying the one corner of Hartle- 

 bury Common, and their .territories in the 

 aggregate covered some fifteen acres. The 

 birds obtained part of their food-supply amongst 

 the gorse and in some young scattered oak- 

 trees, and part in an adjoining coppice and on 

 the surrounding arable land. But they were 

 not the sole occupants of this corner of 

 the Common ; other insectivorous species had 

 territories there also — amongst which were 

 Whitethroats, Grasshopper-Warblers, Willow- 



