SUMMARY 211 



tide recedes at the base, and which on this 

 account are denied to the Guillemot, but 

 manifestly it cannot be allowed so much space 

 as the Bunting, for then comparatively few 

 individuals would attain to reproduction. 



Again, the Reed- Warbler inhabits swamps 

 overgrown with the common reed, and in such 

 places insect life is abundant just at the 

 time when the young are hatched. But these 

 swamps cover a comparatively small acreage in 

 the breeding range of the bird, and if each pair 

 were to attempt to establish dominion over an 

 area equal, let us say, to that of the Willow- 

 Warbler, the species would have but a poor 

 chance in the struggle for existence. So that, 

 in a case of this description, the supply of food 

 and the comparative scarcity of breeding stations 

 have been factors of like importance in the 

 evolution of the territory. 



Finally we were led to inquire as to how 

 it comes about that the extent of the area 

 occupied by each individual is adapted to the 

 circumstances in which the individual finds 

 itself ; and we came to the conclusion that the 

 movements of the bird, subsequent to the 

 initial act of establishing itself in a position, 

 are regulated and defined by the law of habit 

 formation. For example, the Warbler, in 

 response to its inherited nature, takes up a 

 position in an appropriate situation. It then 

 proceeds to search for food ; it makes short 

 journeys first in this direction and then in 

 that ; it repeats these journeys, and gradually 



p 



