_Cursores_[15] (runners). Birds of this class run rather than fly, have no keel on the breast bone, no well developed wings, and their feathers are loosely put together, without the connecting barbs that strengthen the wing feathers of others. But they have strong legs, and feet with nails rather than claws. The Ostrich is most distinguished for its size, strength, speed, and peculiar feathers. The Emeu and Apteryx belong to the same class, the latter being tailless. _Grallatores_[16] (waders). These aquatic birds are distinguished by their very long, bare legs, also necks and bills of like proportions. Herons, Storks, and Flamingoes are representatives. The latter is a peculiar bird, common in some portions of America, Southern Europe, Asia, and Africa. When walking erect it is about five feet high, the body of a light color, and the wings red. When a number go in single file, as such birds do, they appear like a company of British soldiers in uniform. As their legs are quite too long for convenience when incubating, they construct, of grass, rushes, and mud, a little cone of sufficient height, make their nest on the top, and sit astride, the long legs hanging down the sides. This also protects the eggs and young from moisture in wet weather. [Illustration: THE ALBATROSS.] _Natatores_[17] (swimmers). Aquatic birds being keel breasted, with short legs, webbed feet, and thin, light, warm covering, delight in swimming. Some of these have also good flying qualities, as Wild Geese, Swans, Sea-Gulls, and Petrels, which spend much time in skimming over the water, either on or above the surface. This family includes the wandering Albatross, which is among the largest of the sea birds, having from ten to fifteen feet expanse of the wings, and weighing from twenty to thirty pounds; yet it sustains itself in the air for many hours together without any apparent difficulty. It is often met far out at sea, and sailors have many superstitions respecting it. Like all petrels and sea-gulls, the albatross makes its nest on crags and cliffs along the coast, choosing places that seem inaccessible. To gather the eggs of seafowls, which are esteemed a delicacy, and to capture the birds themselves for the feathers, is one of the most perilous employments. The adventurous fowlers are swung over precipices from five hundred to a thousand feet above the sea, sustained simply by a rope, that, by breaking, or slipping from the hands that hold it, must hurl them to certain destruction.