UTILITY OF BIRDS IN WOODLANDS. 105 ~ 
rollers are sought out. The gall insects are dragged from 
their hiding places by Jays and Grosbeaks. Titmice get the 
bud worms, and Woodpeckers search out the fruit worms. 
When the spanworms, disturbed by the movements of the 
caterpillar-hunting Warblers, Vireos, and Sparrows among 
leaves and twigs, spin down on their gossamer threads, and 
so escape one class of enemies, they are marked by Fly- 
catchers sitting on the watch or hovering in the air ready 
to dart upon them. When the mature insects, gaining wings, 
attempt to escape by flight, they are snapped up by these 
same Flycatchers, that sit waiting on the outer limbs of the 
‘trees; or, escaping these, they are pursued by Swallows 
and Swifts in the upper air. Those whose flight is noc- 
turnal must run the gauntlet of the Screech Owl, Night- 
hawk, and Whip-poor-will. Each family of birds seems 
exactly fitted for the pursuit and capture of insects that 
feed on a certain part of the tree, while nearly all species 
can so adapt themselves, at need, as to feed readily on 
insects not ordinarily taken by them. 
While living in the woods, much of the time alone, “for 
several seasons, I have been greatly impressed by both the 
vast yearly uprising of insect pests and the strong repressive 
influence exerted by birds upon their increase. When the 
buds open in spring, broods of tiny, hungry caterpillars 
emerge, only to be preyed upon by the constantly increasing 
flights of birds that peer, swing, flutter, or hop from twig 
to twig through all the woods. At this time these caterpil- 
lars are not at all noticeable, and are very difficult to find ; 
still, the great majority of them are readily found and eaten 
by birds, and therefore never become apparent to ordinary 
observation. As summer comes and the caterpillars grow 
in size, each brood is reduced in number, until, as they ap- 
proach full size, a band which erstwhile numbered hundreds 
of little crawlers has shrunk to a score or two, a “baker’s 
dozen,” or even less. When the survivors pupate they are 
still attacked by birds, and the moths or butterflies as they 
emerge and try their wings are pursued by their swifter 
feathered enemies. 
In studying the increase of the gipsy moth it was found 
