of the Birds of Ireland. 265 



sphere, resort. The geographical position of the island also 

 renders it occasionally the first European land on which 

 North American species, after having crossed the Atlantic, 

 alight. 



Considerable differences, too, consequent on physical causes, 

 will be found to exist in the economy of the same species in 

 Great Britain and Ireland. 



The physical geography, or natural features of the country, 

 compared with those of Great Britain, cannot be said to de- 

 prive Ireland of more than one species (the ptarmigan). The 

 relative proportion, in the two countries, of land to water, 

 of heaths and bogs, to cultivated grounds and plantations, has 

 influence only on the number of individuals. 



Nor does the difference in the mineralogical structure of 

 Ireland, compared with Great Britain, affect the actual pre- 

 sence of any species, although it is the primary cause which 

 influences the number of individuals prevailing in different 

 parts of the island. The plants which appear on particular 

 soils attract such land birds as feed upon their seeds. The 

 submarine rocks and grounds, on which sea -weeds grow plen- 

 tifully, so as to afford shelter to the minute fishes, and the 

 molluscous cretaceous animals on which the wading and 

 swimming birds feed, tempt them in greater numbers to the 

 neighbouring shores. The oozy, the sandy, the gravelly, the 

 stony, the rocky beach, has each its favourite species, as has 

 every peculiar natural or artificial feature of a country, from 

 the level of the sea to the most lofty mountain summit. 



The difference in climate between Ireland and Great Bri- 

 tain, cannot be said to deprive the former island of any spe- 

 cies found in the latter. The comparative mildness of winter 

 in the more western island has, however, great influence on 

 birds. Even in the north of Ireland, a few land species, con- 

 sidered as birds of passage in England, except in the extreme 

 south, become resident ; and some grallatorial birds remain 

 throughout the winter ; although found only in the south of 

 England at this season. The soft-billed birds also, being 

 generally able to procure abundance of food, are, by the com- 

 paratively high temperature, more inclined to song at this 

 period of the year. The humidity of the climate, together 



