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 community, 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 assembling together to breed; for if the different pairs which go to make up the rookery were to scatter throughout the surrounding neighbourhood, 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 protection 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,
