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 span worms, 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 diflScult 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 buttei-flies 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 



