Page:Natural History, Birds.djvu/92

Rh nature: to them appears intrusted the subjugation of those innumerable minute insects which lurk within the buds, the foliage, or the flowers, of plants, and, thus protected, escape that destruction from Swallows to which they are exposed only during flight. The diminutive size of such insects renders them unfit for the nourishment of the Thrushes and the larger insectivorous birds; while their number and variety only become apparent when the boughs are shaken and their retreat disturbed. How enormous, then, would be their multiplication, had not nature provided other races of beings to check their increase. No birds appear more perfectly adapted for this purpose than are the Warblers." Mr. Swainson goes on to notice the arrival of these birds in spring, when the increasing warmth is calling the insect world into renewed life and activity, and their departure in autumn, when the hosts of minute insects begin to diminish, and no longer require to be kept within bounds. As different localities seem allotted to different tribes of insects, so similar diversity is observable in the haunts of the various groups of Warblers. Thus the Golden-crests and Wood-warblers (Sylvianæ) confine themselves principally to the higher trees, where they search for winged insects among the leaves, or capture them like the Fly-catchers, when attempting to escape. The Reed-warblers and the Nightingales (Philomelinæ) haunt the vicinity of waters, or the more dense foliage of hedges, for insects peculiar to such situations. The Stonechats (Saxicolinæ), on the contrary, prefer dry commons, and wide extended plains, feeding on insects appropriated to those