Professor Beal, of the Department of Agriculture, writes, after a prolonged study, that 76 per cent. of the Bluebird's food "consists of insects and their allies, while the other 24 per cent. is made up of various vegetable substances, found mostly in stomachs taken in winter. Beetles constitute 28 per cent. of the whole food, grasshoppers 22, caterpillars 11, and various insects, including quite a number of spiders, comprise the remainder of the insect diet. All these are more or less harmful, except a few predaceous beetles, which amount to 8 per cent., but in view of the large consumption of grasshoppers and caterpillars, we can at least condone this offense, if such it may be called. The destruction of grasshoppers is very noticeable in the months of August and September, when these insects form more than 60 per cent. of the diet."
It is not easy to tempt Bluebirds to an artificial feeding-place, such as I keep supplied with food for Juncos, Chickadees, Woodpeckers, Nuthatches, Jays, etc.; though in winter they will eat dried currants and make their own selection from mill sweepings if scattered about the trees of their haunts. For, above all things, the Bluebird, though friendly and seeking the borderland between the wild and the tame, never becomes familiar, and never does he lose the half-remote individuality that is one of his great charms. Though he lives with us and gives no sign of pride of birth or race, he is not of us, as the Song Sparrow, Chippy or even the easily alarmed Robin. The poet's mantle envelopes him even as the apple blossoms throw a rosy mist about his doorway, and it is best so.
THE BLUEBIRDS.
1. Eastern Bluebird (Sialia sialis)
Adult male.—Length 7 inches. Upper parts, wings and tail bright blue; breast and sides rusty, reddish brown, belly white. Adult female.—Similar to the male, but upper parts except the upper tail coverts, duller, gray or brownish blue, the breast and sides paler. Nestling.—Wings and tail essentially like those of adult, upper parts dark sooty brown, the back spotted with whitish; below, whitish, but the feathers of the breast and sides widely margined with brown, producing a spotted appearance. This plumage is soon followed by the fall or winter plumage, in which the blue feathers of the back are fringed with rusty, and young and old birds are then alike in color.
Range.—Eastern United States west to the Rocky Mountains; nests from the Gulf States to Manitoba and Nova Scotia; winters from southern New England southward.
1a. Azure Bluebird (Sialia sialis azurea).
Similar to the Eastern Bluebird, but breast paler, upper parts lighter, more cerulean blue.
Range.—Mountains of eastern Mexico north to southern Arizona.
2. Western Bluebird (Sialia mexicana occidentalis).