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.
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.