BRITISH WARBLERS 



But with respect to this law of territory we must still regard a 

 community as one unit, for community rights with community 

 as one individual rights with another. The Books from one 

 rookery will attack those from another, the members of one 

 colony of G-annets (Sulci bassana) will struggle with those of 

 another. And it is possible that the attainment of reproduc- 

 tion may be an even more difficult task for those species that 

 are sociable, since battles occur between individuals with 

 respect to their own particular domain even within the pre- 

 cincts of the territory of a community. At no time are the 

 Books so quarrelsome as when they commence to build their 

 nests, and though the quarrel may be only caused by one 

 stealing nesting material from another, yet they certainly 

 appear to respect one another's rights. But even the stealing 

 of twigs and wool would be similar in its results to a battle, if 

 thereby any particular individual were prevented from breed- 

 ing. Circumstances compel other species to breed together. 

 For many sea-birds breeding stations are few and far between ; 

 nevertheless, even the members of these cliff-breeding species 

 seem to have their own particular territory ; and it must be 

 remembered that not every Gull nor every Guillemot on a 

 ledge of rock is a breeding bird. The working of the law of 

 territory is a beautiful illustration of adaptation, since a 

 territory is developed in some instances to ensure an ample 

 supply of food for the helpless young, while in others it is 

 gradually limited in extent to ensure reproduction, but in 

 every case perfected so as to hamper in no way, but rather 

 improve the position of the species in relation to the struggle 

 for existence. Thus scarcity of breeding stations, scarcity or 

 abundance of certain types of food, and the relation between 

 the supply of food and the localities suitable for breeding 

 purposes must have been taken into consideration as species 

 arose and adjustments were made accordingly. If the indi- 

 viduals of any one species were to develop a territory larger 

 than was necessary, and by so doing prevent a portion of their 

 own community from breeding, that species would gradually 



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