Page:Territory in Bird Life by Henry Eliot Howard (London, John Murray edition).djvu/269

Rh 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