184 MIGRATION OF BIRDS. 



the globe, indigenous to certain sites, and neither 

 driven there by the increased multitudes of their 

 fellows, nor the intrusions of man, but created for, 

 and located to, a certain region, where alone they 

 find congenial food, temperature, or some undefin- 

 able accordance fitting for their constitutional me- 

 chanism. Creatures habituated to a cold northern 

 district, or the products and warmth of a solar 

 clime, if driven southward or northward by any 

 impulsive power, would pine, diminish, and ulti- 

 mately perish : an alpine or a lowland creature 

 would probably be very rarely able to support a 

 mutual change of situation without deterioration, or 

 gradual extinction ; but where certain regions or 

 countries similarly constituted become exhausted of 

 their natural inhabitants by accident or by local 

 acting causes, they seem universally to be resettled 

 by the surplus of another, and uninhabited tracts 

 become tenanted by families impelled to migrate by 

 superior force or rival jealousy. 



The tall tangled hedgerow, the fir grove, or the 

 old, well- wooded inclosure, constitutes the delight 

 of the magpie (corvus pica), as there alone its large 

 and dark nest has any chance of escaping observa- 

 tion. We here annually deprive it of these asylums, 

 and it leaves us ; but it does not seem to be a bird 

 that increases much any where. As it generally 

 lays eight or ten eggs, and is a very wary and cun- 

 ning creature, avoiding all appearance of danger, it 

 might be supposed that it would yearly become 

 more numerous. Upon particular occasions we see 



