and kingfisher (Fig. 58) catch and eat fish for food, yet a glance at the two figures shows how unlike in form these two birds are.

A second scheme of classification is that based upon their habitat. Thus we may speak of water birds, shore birds, marsh birds, and land birds. This plan, too, may group together birds strikingly unrelated in structure and habits, as becomes clear when we compare two land birds like the hawk (Fig. 64), and the sparrow (Fig. 70).

57. Scientific classification of birds.

Modern scientific classi

fication divides the birds of North America into seventeen groups or

FIG. 60.-Blue heron. (Wright's "Citizen Bird.")

orders, all the birds of a given order resembling each other more or less in structure. The common names given to some of these orders are suggested by their habits. As examples we may name diving birds (loon), long-winged swimmers (gulls and terns), scratching birds (hens, turkeys, and quails), birds of prey (eagles, hawks, and owls), and woodpeckers (downy woodpecker). The highest order, known as the perching birds, is divided into twenty families, some of which are the crow family, the sparrow family, the warbler, and the

thrush family. The total number of species of the perching birds is far greater than that of all other species taken together. We shall now group together a few of the more closely related orders, and discuss somewhat their characteristic adaptations of structure.

58. Webfooted birds (swimming birds). In this group we include several orders of birds that have webbed feet, which fit them

for swimming in the water. Common examples of such birds are ducks, geese, albatross, and gulls (Fig. 59). Near the tail region of most of these birds an oil gland is developed, from which the bird obtains the oil that it uses in keeping its feathers from getting water-soaked; this is likewise true of all other birds. As one would expect, a large number of these

species feed upon fish and other water animals.

59. Wading birds. - All the birds in this group have long, slender legs, which adapt them for wading out into the water for food. Such birds are the herons (Fig. 60), egrets, storks, and cranes. The flamingoes (Fig. 61) have webbed feet like swimming birds, and so they are regarded as connecting links between swimming and wading birds.

60. Scratching birds. This group includes the domesticated chicken and turkey and the quail (Fig. 62). All our various forms of chickens are descended from the

small jungle fowl of India (Fig. 63). The wild turkey still exists in some parts of our country, but it is being rapidly exterminated by hunters. The toes of all the scratching birds are armed with strong, blunt nails, by which they are enabled to dig in the soil for insects and worms. All these birds, too, feed to some extent upon grain.

61. Birds of prey. The hawks (Fig. 64), eagles, and owls (Fig. 65), which comprise this group have acquired the name of birds of prey from their habit of catching and feeding on rats, mice, birds, and other animals. Their feet are armed with sharp incurved claws, and the upper part of their bills is hooked; and so they are specially adapted for seizing and tearing their prey.

62. Woodpeckers. These birds are admirably adapted to creep and climb up the trunks of trees, for they have two clawed toes extending forward, and two backward, and their tail feathers are so stiffened that they serve as props against the bark when the bird is resting (Fig. 66). The food of the woodpeckers is largely composed of insects, which these birds secure by digging them out of the

63. Perching birds. This order, as we have said before, contains by far the largest number of species of birds. All these birds are specially adapted for holding to the limbs of trees, since the mechanism of the leg is so arranged that the toes are automatically clutched to the support upon which the bird is sitting. In this group are included practically all of our bird vocalists, hence the perching birds are often called the " song birds." Among the most beautiful of our songsters are the bobolinks (Fig. 67), catbird, and thrushes (Fig. 68).

The young of all the perching birds, for weeks after they are