200 TERRITORY AND REPRODUCTION 



suitable breeding ground, no greater calamity 

 could befall the species than that some members 

 should exercise dominion over too large an area 

 of the habitable part of the cliff and thus 

 prevent others from breeding. Under such 

 conditions the race could not endure, since in 

 this, as in every case, its survival must depend 

 upon a close correspondence between the 

 behaviour of the individual and the circum- 

 stances in the external environment. 



Scarcity of suitable cliffs is the principal 

 reason of the ledges being so closely packed 

 with Guillemots, just as it accounts for this 

 part of the precipice being crowded with Kitti- 

 wake Gulls, that part with Herring-Gulls, and 

 that part again with Razorbills and Puffins. 

 Yet each individual preserves its few square 

 feet of rock or soil from molestation, and the 

 area each one occupies varies according to the 

 conditions of existence of the species. Thus 

 the Herring-Gull occupies a comparatively small 

 area, although one many times larger than that 

 of the Guillemot. It requires more space than 

 the latter, owing to the fact that it not only 

 builds a nest but rears four instead of a single 

 offspring, and it can be allowed this, because, 

 since its young remain in the nest until they are 

 capable of sustained flight, it can make use of 

 many miles of cliff from which the tide recedes 

 at the base, or which have, at their ba,se, 

 rocks jutting out into the sea ; but manifestly 

 it cannot be allowed so much space as the 

 Bunting. 



