Think of what the birds are doing on every farm, in every garden, and about every home in the land. Think of the millions of beautiful wings, of the graceful and attractive figures, of the cunning nests, and of the singing throats! Do you think that the whole service of the birds is to be beautiful, to sing charmingly, and to rear their little ones? By no means is this their chief service to man. Aside from these services the greatest work of birds is to destroy insects. It is one of the wise provisions of nature that many of the most brilliantly winged and most enchanting songsters are our most practical friends. Not all birds feed on insects and animals; but even those that eat but a small amount of insect food may still destroy insects that would have damaged fruit and crops much more than the birds themselves do. As to their food, birds are divided into three general classes. First, those that live wholly or almost wholly on insects. These are called insectivorous birds. Chief among these are the warblers, cuckoos, swallows, martins, flycatchers, nighthawks, whippoorwills, swifts, and humming-birds. We cannot have too many of these birds. They should be encouraged and protected. They should be supplied with shelter and water. Birds of the second class feed by preference on fruits, nuts, and grain. The bluebird, robin, wood thrush, mocking-bird, catbird, chickadee, cedar-bird, meadow lark, oriole, jay, crow, and woodpecker belong to this group. These birds never fail to perform a service for us by devouring many weed seeds. [Illustration: FIG. 280. A KINGBIRD] The third class is known as the hard-billed birds. It includes those birds which live principally on seeds and grain--the canary, goldfinch, sparrow, and some others. Birds that come early, like the bluebird, robin, and redwing, are of special service in destroying insects before the insects lay their eggs for the season. The robins on the lawn search out the caterpillars and cutworms. The chipping sparrow and the wren in the shrubbery look out for all kinds of insects. They watch over the orchard and feed freely on the enemies of the apple and other fruit trees. The trunks of these trees are often attacked by borers, which gnaw holes in the bark and wood, and often cause the death of the trees. The woodpeckers hunt for these appetizing borers and by means of their barbed tongues bring them from their hiding-places. On the outside of the bark of the trunk and branches the bark lice work. These are devoured by the nuthatches, creepers, and chickadees.