202 TERRITORY AND REPRODUCTION 



dominion over too large an area, the species as 

 a whole would suffer. 



In all these examples, the fact of different 

 individuals being in such close proximity may 

 afford some protection from enemies both as 

 regards the egg and the offspring, and in so far 

 as there is a mutual advantage such assemblages 

 may be spoken of as communities. A com- 

 munity, however, in the true sense of the word, 

 is a collection of individuals brought together, 

 not primarily as a result of shortage of breeding 

 ground, but in consequence of advantages of 

 communal ownership over individual ownership. 

 A rookery is an example of a true community. 

 Neither shortage of nesting accommodation nor 

 scarcity of food can account for Rooks assem- 

 bling together to breed ; for if the different 

 pairs which go to make up the rookery were to 

 scatter throughout the surrounding neighbour- 

 hood, they would, as a rule, find plenty of trees 

 in which to build their nests, and plenty of food. 

 How, then, can the theory apply to a species 

 that breeds under such conditions ? What part 

 can the territory play in furthering the life of 

 the individual when large numbers of nests are 

 built closely together in the same tree ? There 

 is much evidence to show that mutual protec- 

 tion is a necessary condition of the Rook's 

 existence ; many cases are on record of rookeries 

 being destroyed by Carrion-Crows, Hooded 

 Crows, and Ravens. For instance, Mr Ward 

 Fowler records a case in which a pair of Crows 

 attacked a small rookery, ransacked the nests, 



