The Spell of the Rockies by Enos A. Mills

Although the eagle has the emblematic place of honor in the United States, the downy woodpecker is distinguished as the most useful bird citizen. Of the eight hundred and three kinds of birds in North America, his services are most helpful to man. He destroys destructive forest insects. Long ago Nature selected the woodpecker to be the chief caretaker -- the physician and surgeon -- of the tree world. This is a stupendous task. Forests are extensive and are formed of hundreds of species of trees. The American woodpeckers have the supervision of uncounted acres that are forested with more than six hundred kinds of trees.

With the exception of the California big tree, each tree species is preyed upon by scores, and many species by hundreds, of injurious and deadly insects. Five hundred kinds of insects are known to prey upon the oak, and a complete count may show a thousand kinds. Many of these insects multiply with amazing rapidity, and at all times countless numbers of these aggressive pests form warrior armies with which the woodpecker must constantly contend.