238 REPORT OF THE FOREST, FISH AND GAME COMMISSION. 



destruction by birds as many writers have supposed. Many species that have a 

 disgusting odor, and rank, acrid taste, were formerly thought to be protected 

 by these means, but it is found that these insects often form a very important 

 percentage of the food of birds, and are eaten to some extent by nearly all 

 insectivorous species. 



In seeking for food, birds destroy useful insects as well as harmful ones; and 

 while in many cases this is to be deplored, yet in the long run the birds are doing 

 a good service by this indiscriminate destruction. Investigation and observation 

 have furnished grounds for the belief that the true function of the insectivorous 

 birds is to reduce the too crowded ranks of insect life as a whole, rather than to 

 prey upon this or that particular pest, although this may be a very welcome 

 service. If birds ate only harmful vegetable-eating insects, the predaceous species, 

 which also prey upon them, would have their food supply reduced, and as it is 

 well-known that many of them can and do feed to some extent upon vegetable 

 matter, they might in their search for food attack some valuable products of the 

 farm, orchard, or forest, and so in their turn become as great a pest as was their 

 former prey. The woodpeckers feed largely upon woodboring grubs, the cukoos 

 and orioles subsist upon caterpillars, all of which are practically harmful insects, 

 while the flycatchers prey to a great extent upon parasitic Hymenoptera, which 

 would otherwise live upon the grubs and caterpillars, so that these groups of birds 

 complement each other in their food habits, the one devouring the pests upon 

 which the prey of the other would have subsisted. 



While many birds belonging to various families gain their living largely from 

 tree-infesting insects, there are some families of which every species practically 

 lives upon trees, and subsist upon the insects or other food which they find there. 

 At the head of these may be placed the family of woodpeckers (Picidae) and fol- 

 lowing these, but scarcely inferior in rank of usefulness, are the titmice (Paridae), 

 the creepers (Certhiidae), the kinglets (Silviidae), the vireos (Vireonidae), and the 

 wood warblers (Mniotiltidae). To these may be added certain species of wrens, 

 orioles, flycatchers and swallows, of which many species subsist to a very consider- 

 able extent upon arboreal insects. In the following pages all references to the 

 contents of birds' stomachs, unless otherwise stated, are based on examinations 

 made by the writer. 



The Woodpeckers. 



Among birds which decidedly affect the welfare of the forest the family of 

 woodpeckers probably takes the Lead. Of these there are about forty-five species 

 and subspecies that are found within the limits of the United States, all of 

 which are of decidedly economic importance. The value of their work in dollars 



