CHANGE OF BIRDS. 333 



many of the birds that are probably with accuracy 

 described as having been confined to the southern parts 

 of England, are now met with in the north, and also in 

 the cultivated parts of Scotland. The plover comes in 

 place of the grouse, the partridge in place of the 

 plover, and where coppices become abundant, the 

 pheasant, in turn, invades the dominions of the par- 

 tridge. The trees and plants with more succulent 

 leaves, that cultivation introduces, instead of the heath, 

 the hard grass, the furze, the broom, and all those 

 native vegetables of the north that have austere juices, 

 necessarily bring along with them a vast number of 

 insects. We say " necessarily ;" for wherever the 

 proper food for any of the productions of nature is to 

 be found, thither will that production come to it, 

 by means that no one can find out ; as for instance, 

 if roses or cherries are introduced, there are sure to 

 be aphides ; if any of the brassicas, there are sure to 

 be caterpillars ; and if there be even an introduction 

 of nettles, their beautiful butterfly s will visit them. 

 When they have increased to a certain amount, they 

 are sure to bring, not only those resident birds that 

 feed themselves and their young upon larvse, but also 

 the warblers and other summer visitants. It is not 

 the finer climate that causes the nightingale to cheer 

 only the south of England with its song in the summer ; 

 it is the more abundant supply of soft caterpillars, 

 of food fitted for the young ; and though it is not 

 possible by any cultivation wholly to equalize the 

 temperature over even the limited extent of Britain, 

 yet that equalization has been very much approximated 

 of late years ; and a community of animals has 



