How have the various types of bird life come into existence? To understand this we must study the wings of the creature to learn its evolution from the early reptile-like type of bird. The most primitive use of the wing is as a hand, by which the bird may climb about. In contrast the albatross has the finest developed wings of any species which are fourteen feet across. The man-o'-war, however, is even a better example, perhaps, for although having a body no larger than a hen, it has wings which spread apart to a distance of seven or eight feet, enabling it to soar in the air for several days without touching the earth. By intertwining the outer feathers of the wings some birds can remain stationary in the air for hours at a time, not once moving a wing. The razor-billed hawk is the nearest living representative of the extinct great hawk, a bird which, having small wings, could not fly, and soon became extinct. The penguin, with its flippers, can fly only on the water, and has to waddle when on land. Certain grebes which find their food in lakes have also lost their power of flight. This is true of some pigeons, auks, parrots, grebes, ducks and other birds which have not found it necessary to obtain their food by flying. Wings are also used to express emotion. Many young birds, of which the oriole furnishes an example, cause their wings to quaver in supplication. Certain birds also make use of their wings as a musical organ, as is evinced in the whistling sound produced by the woodcock. Our nighthawk makes a booming sound with its wings by extending its outer quills as it dives earthward. A weapon is also found by some birds in their wings, the pigeon, hen and other of our common birds using their wings to strike with. The foot shares with the wing the duties of locomotion. Birds with highly developed wings have poor feet. The swallow, an aerial bird, is an example. The chimney-swift has a tiny foot, but enormously developed wings, and if placed on a flat surface is unable even to support itself. All aquatic and terrestrial birds have excellently developed feet. The loon is so thoroughly aquatic that it cannot walk on land without the support of its breast and wings. The sea snipe has a foot especially fitted for swimming, and can be found a few hundred miles off the Atlantic coast in flocks of hundreds of thousands, perfectly at home in the water. The foot is generally related to the length of the neck. The flamingo wades out into the water, and is able to duck its head and secure its food with the aid of its particularly constructed neck. In securing prey the foot also plays an important part. The great horned owl and the duck hawk have enormous grasping power in their claws. In our grouse or partridge a horny, fringe-like growth appears on the toes late in the fall, serving as a sort of snowshoe during the winter, by which the bird is enabled to walk on the surface of the snow. This growth is shed in the spring.