2 
Conservation Bulletin 18 
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 vege¬ 
table food, as the seeds of weeds. Here again is another useful func¬ 
tion 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 sub¬ 
species, 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 refer¬ 
ence to the data on which they are based. 
THE BLUEBIRDS 
The eastern bluebird 3 (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. 
The bluebird has not been accused, 
so far as known, of stealing fruit or 
of preying upon crops. An examina¬ 
tion of S55 stomachs showed that 68 
per cent of the food consists of in¬ 
sects and their allies, while the other 
32 per cent is made up of various 
vegetable substances, found mostly in 
stomachs taken in winter. Beetles 
constitute 21 per cent of the whole 
food, grasshoppers 22, caterpillars 10, 
and various other insects 9, while a 
number of spiders and myriapods, 
about 6 per cent, comprise the re¬ 
mainder of the animal diet. All 
these are more or less harmful, ex¬ 
cept a few predacious beetles, which amount to 9 per cent. In view of the large 
consumption of grasshoppers and caterpillars, we may at least condone this 
offense, if such it may be called. The destruction of grasshoppers is very 
noticeable in August and September, when these insects make up about 53 per 
cent of the diet. 
It is evident that in the selection of its food the bluebird is governed more 
by abundance than by choice. Predacious beetles are eaten in spring, as they 
are among the first insects to appear; but in early summer caterpillars form 
an important part of the diet, and these are later replaced by grasshoppers. 
Beetles are eaten at all times, except when grasshoppers are more easily 
obtained. 
So far as its vegetable food is concerned the bluebird is positively harmless. 
The only trace of any useful product in the stomachs consisted of a few black¬ 
s Sialia sialis. 
