Page:Popular Science Monthly Volume 42.djvu/473

 Rh into gray, but easily distinguished by the white-edged tail that it flirts open when started from the dusty highway or flitting before us along the fence-rows. In old fields and pastures the darker-streaked savanna sparrow and the little earth-colored grasshopper sparrow with its yellow-edged wings and dry, cricket-like song, start out of the grass beneath our feet; and if in June days we search long and patiently, a glimpse of a nest and its treasures may reward our pains.

Every one knows the meadow lark stalking over fields of short grass or swiftly rising from weedy cover with sharp note of alarm; the bobolink with throat full of song hovering above the lush meadows and acres of waving herd's grass or gathering in dense autumnal flocks among the river reeds; the swamp blackbird with its brilliant epaulets of red; the shore lark and titlark—all these are birds of the open, grass-grown fields.

Glancing at a physical map of North America we see that the continent is characterized by regions of widely different aspect. By far the largest area is forest clad, including the vast territory east of the Mississippi Valley and the great portion of British America. West of this, and extending from the Gulf and the Mexican highlands northward to the Athabasca River, is the region of the great plains, rolling, grass-covered prairies, dry and treeless, except in the river bottoms of the eastern portion. To the west the plains rise into the greater plateau of the continent, a steppe region crowned by the lofty, pine-clad ranges of the Rocky Mountain system. Between this and the Sierra Nevada ranges lies an alkaline waste, the Great Desert Basin, while along the Pacific slope a forest region again prevails.

It is evident, from this hasty view of the entire continental area, that we have before us precisely the same factors, though on