CONTENTS
| 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] |
W
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.
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 life 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.
The eastern bluebird[2] ([fig. 1]), one of the most familiar and welcome of our feathered visitors, is a common inhabitant of all the States east of the Rocky Mountains from the Gulf of Mexico to southern Canada. In the Mississippi valley it winters as far north as southern Illinois, and in the East as far as Pennsylvania. It is one of the earliest northern migrants, and everywhere is hailed as a harbinger of spring. Very domestic in habits, it frequents orchards and gardens, and builds its nests in cavities of trees, crannies in farm buildings, or boxes provided for its use.