They are usually divided into three great families: Falcons, Vultures, and Owls. The first includes all kinds of Hawks and Eagles. True falcons reveal a predatory character, not only by their general structure as described, but have a special arrangement for keeping their formidable weapons in order. The continual sharpness of their claws is necessary, and to maintain it they must be kept from coming in contact with hard substances. To make this practicable, though they are not retractile, like a cat’s claws, there not being sufficient integuments to cover them, the bird has power to elevate their points when stepping or perching on anything likely to dull them. Being very powerful and rapid flyers, falcons were in former times tamed, and trained for catching other birds and small game. Falconry, in the middle ages, was one of the principal diversions of kings and noblemen, lords and ladies, and in later times the same sport was practiced in England under the name of “hawking.” The training of the birds was a profession, and there were teachers who became proficient in it. The Eagle, king of birds, belongs to this class; he is, perhaps, inferior in activity and enterprise, but is more powerful, and his supremacy is undisputed. The Bald Eagle adorns our American flag, and is a fit emblem of national sovereignty, though there was, it is confessed, some ground for Franklin’s protest, “The bird has a bad moral character, and does not get his living honestly.” The Gypætos, or Vulture Eagle, is the largest bird of Europe, and often a terror to the peasants near the Pyrenees and Swiss Alps. Its great strength, bold, predatory habits, and impetuosity in pouncing on animals exceeding itself in size, make it more formidable than most eagles are. [Illustration: THE FLAMINGO.] Vultures are cowardly, disgusting creatures, and feed mostly on putrid flesh, yet they are useful scavengers in hot climates, devouring much animal matter that would otherwise cause pestilence and death. Owls are nocturnal birds of prey, and though seldom abroad except in the darkness, or twilight, being often captured and confined, they are pretty well known. _Insessores_[14] (perching birds). This term is adopted as vaguely descriptive of many species, of which no particular mention can be made. They include our common singing birds and skillful nest builders. Some of these build low, among the grass, others on branches of trees. Some are solitary, and during the nesting season isolate themselves. Others, as the “sociable weavers,” unite in building them cities, in which each pair claims a private residence.