THE HEDGE WARBLER. 375 



food has as much influence upon the character of animals as 

 difference of soil has upon those of vegetables, it would be of 

 much importance, as well in the individual history of birds 

 as in the physiology of animals generally, to see what influence 

 that difference in the early feeding has upon the future habits 

 of the bird. The probability from the analogy of domesti- 

 cated poultry is, that that treatment when young tempers 

 them more to the climate ; and that, as the country becomes 

 more and more improved by drainage and culture, those birds 

 which now retire during the winter, may remain the whole 

 year. Consequently, the appearance of those birds more 

 northerly or upland than they had wont to come, is a testi- 

 mony of what cultivation has already done towards the 

 increased productiveness and salubrity of the place, in which 

 they sport and sing for the first time. 



Birds, and those insects upon which birds feed, are as true 

 to climate and fertility as the vegetable tribes are. The 

 summer butterfly or moth, and the summer bird, are alike 

 children of the sun ; and, if they come into any place in 

 which they were not previously to be found, we may rest 

 assured that some change favourable both to the subsistence 

 and the health of man has been effected there ; that some 

 diminution lias taken place in that evaporation from bog and 

 marsh which chills, stunts, and sours the vegetation, and 

 nourishes carex and rushes, with their accompanying mosses, 

 and all the elements of peat-bog, and that the earth is in 

 a condition to feel and to profit by the whole influence of the 

 season, nursing a more sweet and kindly vegetation upon 

 which the caterpillar can feed ; and where these again can 

 supply food for the warblers and their broods. 



That all these birds are now spreading northward and 

 upland, there can be little doubt, independently of the greater 

 attention which (on the part of some) has been paid to the 

 feathered tribes. That alone would not explain the differ 



