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 BLUEBIRDS. 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. [2] _Sialia sialis_. [Illustration: Fig. 1.--Bluebird. Length, about 6½ inches.] The bluebird has not been accused, so far as known, of stealing fruit or of preying upon crops. An examination of 855 stomachs showed that 68 per cent of the food consists of insects 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 remainder of the animal diet. All these are more or less harmful, except 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.