Within certain limits birds eat the kind of food that is most accessible, especially when their natural food is scarce or wanting. Thus they sometimes injure the crops of the farmer who has unintentionally destroyed their natural food in his improvement of swamp or pasture. Most of the damage done by birds and complained of by farmers and fruit growers arises from this very cause. The berry-bearing shrubs and seed-bearing weeds have been cleared away, and the birds have no recourse but to attack the cultivated grain or fruit which have replaced their natural food supply. The great majority of land birds subsist upon insects during the period of nesting and moulting, and also feed their young upon them during the first few weeks. Many species live almost entirely upon insects, taking vegetable food only when other subsistence fails. It is thus evident that in the course of a year birds destroy an incalculable number of insects, and it is difficult to overestimate the value of their services in restraining the great tide of insect life. In winter, in the northern part of the country, insects become scarce or entirely disappear. Many species of birds, however, remain during the cold season and are able to maintain bike by eating vegetable food, as the seeds of weeds. Here again is another useful function of birds in destroying these weed seeds and thereby lessening the growth of the next year. In the following pages are discussed the food habits of more than 50 birds belonging to 12 families. Many are eastern forms which are represented in the West by slightly different species or subspecies, but unless the food habits differ they are not separately described. In some cases specific percentages of food are given, but for the most part the statements are made without direct reference to the data on which they are based.[1] [1] Farmers’ Bulletins describing the food habits of wild birds and groups of birds, or presenting methods of attracting them about our homes have been issued as follows: 54. Some Common Birds in their Relation to Agriculture, by F. E. L. Beal, 1897. The present bulletin is largely a revision of this bulletin and supersedes it. 383. How to Destroy English Sparrows, by Ned Dearborn, 1910. This bulletin has been superseded by Farmers’ Bulletin 493. 450. Our Grosbeaks and Their Relation to Agriculture, by W. L. McAtee, 1911. 493. The English Sparrow as a Pest, by Ned Dearborn, 1912. 497. Some Common Game, Aquatic, and Rapacious Birds in Relation to Man, by W. L. McAtee and F. E. L. Beal, 1912. 506. Food of Some Well-known Birds of Forest, Farm, and Garden, by F. E. L. Beal and W. L. McAtee, 1912.