Page:Popular Science Monthly Volume 51.djvu/383

Rh straggle along the southern edge of the inhospitable Barren Grounds of arctic America—a treeless, blizzard-swept waste of mosses and saxifrages, the home of the wolf, the musk ox, and the Barren Ground caribou, stretching away to the shores of the Arctic Ocean.

Zoölogists recognize several well-defined regions within these life zones, each of which is characterized by some forms of reptiles, birds, and mammals that do not range or breed beyond its limits. These geographical life areas have received the name of faunas. In the eastern United States four such regions are recognized and are known as the Canadian, Alleghanian, Carolinian, and Louisianian faunas. The Canadian fauna belongs to the boreal region. It is characterized by certain species of mammals that do not range south of it, as the moose, caribou, and wolverine, and by certain birds that breed within its borders. Among these latter are the well-known snowbird, several species of wood warblers, the winter wren, and the hermit thrush. This fauna extends southward to Georgia along the hemlock-crowned crests of the Appalachians, where the altitude produces conditions similar to those prevailing in the coniferous forests of the boreal zone to the north. Through the deep, cool shades of these hemlock woods floats the song of the hermit thrush—a vesper strain that falls on the sense like the tinkling of some far-off, sweet-toned bell, rising and swelling in an amplitude of liquid melody that fills the twilit aisles and dies away in still solitudes. The pleasing song of the snowbird breaks upon the forest stillness, quite different from its sharp, clicking notes so familiar in our winter walks about home. Along the brawling mountain brooks and trout streams of the Alleghanies the water thrush, with oddly jerking motions, bobs up and down on the rocks, and the winter wren flits about the windfalls or steals away from its nest, that is hidden under the gnarled roots of some old stump that overhangs the bank. To an ornithologist these and other features indicate a decided Canadian tinge in the summer bird fauna of the higher ranges from the Catskills to Georgia.

The so-called Alleghanian fauna of the eastern transition zone includes all the more familiar species of birds, reptiles, and mammals inhabiting the New England and Middle States and the lower ranges of the Appalachian highland to the south. Its chief characteristic is a mingling of the life of the other two zones—the boreal and the austral. Such decidedly northern forms as the bay lynx or catamount, the red squirrel, porcupine, woodchuck, chipmunk, jumping mouse, and certain other mammals find their ranges restricted along the southern boundary of this fauna. A number of familiar birds, as the brown thrasher, scarlet tanager, bluebird, house wren, chewink, indigo bird, meadow lark, the