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 plentifully so as to afford shelter to the minute fishes, and the molluscous and crustaceous 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 Britain cannot be said to deprive the former island of any species 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, considered 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 Eugland at this season. The soft-billed birds also being generally able to procure abundance of food, are by the comparatively high temperature, more inclined to song at this period of the year. The humidity of the climate, together with the great extent of bog throughout the island, brings hither to winter, different species of grallatorial and other birds, in much greater numbers than prevail in England or Scotland. The extent of moist and rich meadows in summer has a similar, but more limited, influence. The want of extensive districts of old timber seems, when fully considered, to have little effect in excluding from Ireland species which inhabit Great Britain.
To the laws of geographical distribution alone must, I conceive, be attributed our want of species not affected by any of the
A 2
