Page. Page. The bluebirds 2 Bullock oriole 14 The robins 3 The meadowlarks 14 The titmice 4 The red-winged blackbirds 15 The wrens 6 Bobolink 17 Brown thrasher 7 Crow 17 Catbird 7 Blue jay 19 The swallows 8 Pacific coast jays 20 Towhee 9 The phœbes 21 The sparrows 9 The kingbirds 23 House finch 11 Nighthawk 24 The grackles 12 The woodpeckers 25 Brewer blackbird 12 The cuckoos 27 Baltimore oriole 13 Bobwhite 28 WHETHER a bird is beneficial or injurious depends almost entirely upon what it eats. In the case of species which are very abundant, or which feed to some extent on the crops of the farmer, the question of their average diet becomes one of supreme importance, and only by stomach examinations can it be satisfactorily answered. Field observations are at best but fragmentary and inconclusive and lead to no final results. Birds are often accused of eating this or that product of cultivation, when an examination of the stomachs shows the accusation to be unfounded. Accordingly, the Biological Survey has conducted for some years a systematic investigation of the food of those species which are most common about the farm and garden. 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-producing shrubs and seed-bearing weeds have been cleared away, and the birds have no recourse but to attack the cultivated grain or fruit which has replaced their natural food supply. The great majority of land birds subsist upon insects during the period of nesting and molting, 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.