18 FORM AND HABIT: THE WING. The young of tins bird have well-developed claws on the tliumb and first finger, and long before they can fly they nse them as aids in clambering abont the bushes, very much as we may imagine the Archfeopteryx did. In the adult these claws are wanting. Some eminently aquatic birds, as Grebes and Pen- guins, when on land, may use their wings as fore legs in scrambling awkwardly along; while some flightless birds, for example, the Ostrich, spread their wings when run- ning. But let us consider the wing in its true ofiice, that of an organ of flight, showing its range of variation, and finally its degradation into a flightless organ. Among flying birds the spread wings measure in extent from about three inches in the smallest Hummingljird to twelve or fourteen feet in the Wandering Albatross. The relation between shape of wing and style of flight is so close that if you show an ornithologist a bird's wing he can generally tell you the character of its owner's flight. The ex- tremes are shown by the short-winged ground birds, Fig. 5.— Short, rounded win^ and largi foot of Little Black Kail, a terres trial bird. (Vs natural size.) Fig. 6.— Long, pointed wing and small foot of Tree Swallow, an aerial bird. (3/6 natural size.) such as Eail, Quail, 'Grouse, certain Sparrows, etc., and lons-wino-ed birds, like the Swallows and Albatrosses. There is here a close and, for the ground-inhabitmg
