The Canadian zone crosses from Canada into the northern parts mammals and birds are the lynx, porcupine, northern red squirrel, varying and snowshoe rabbits, white-throated sparrow, spruce grouse, and Canada jay; within this zone in the North-eastern states are a few moose and caribou.
The Transition zone, in which the extreme southern limit of several boreal species overlaps the extreme northern limit of numerous austral species, is divided into an eastern humid or Alleghanian area, a western arid area, and a Pacific coast humid area. The Alleghanian area comprises most of the lowlands of New England. New York and Pennsylvania, the north-east cor ner of Ohio, most of the lower peninsula of Michigan, nearly all of Wisconsin, more than half of Minnesota, eastern North Da kota, north-eastern South Dakota, and the greater part of the Appalachian Mountains from Pennsylvania to Georgia. It has few distinctive species, but within its borders the southern mole and cotton-tail rabbit of the South meet the star-nosed mole and the varying hare of the North, and the southern bobwhite, bluebird, catbird, chewink, thrasher and wood thrush are neigh bours of the bobolink and the hermit and Wilson's thrushes.
The arid Transition life-zone comprises the western part of the Dakotas, north-eastern Montana, and irregular areas in Wash ington, Oregon, Idaho, Wyoming, California, Nevada, Utah, Colo rado, Arizona, New Mexico and western Texas, covering for the most part the eastern base of the Cascade and Sierra Nevada Mountains and the higher parts of the Great Basin and the plateaus. Its most characteristic animals and birds include the white-tailed jack-rabbit, sage hen and sharp-tailed grouse. The Pacific coast Transition life-zone comprises the region between the Cascade and Coast ranges in Washington and Oregon, parts of northern California, and most of the California coast region from Cape Mendocino to Santa Barbara. It is the home of the Columbia black-tailed deer, western raccoon, Douglas red squirrel, tailless sewellel, Oregon ruffed grouse and Pacific winter wren.
The Upper Austral zone is divided into an eastern humid (or Carolinian) area and a western arid (or Upper Sonoran) area. The Carolinian area extends from southern Michigan to northern Georgia and from the Atlantic coast to western Kansas, compris ing practically all of this region except the highlands and moun tains. It is the northernmost home of the opossum, grey fox, fox
squirrel, cardinal, summer tanager and yellow-breasted chat. The Upper Sonoran life-zone comprises south-eastern Montana and eastern Wyoming; portions of western South Dakota, Nebraska, Kansas and Oklahoma ; north-western Texas, eastern Colorado and south-eastern New Mexico; the lower plains of Utah, Idaho, Washington and Oregon ; and narrow belts in California, Nevada and Arizona. Among its characteristic mammals and birds are the black-tailed jack-rabbit, sage chipmunk, prairie-dog, burrowing owl and sage thrasher.
The Lower Austral zone occupies the greater part of the South ern States, and is divided near the 98th meridian into an eastern humid or Austroriparian area and a western arid or Lower Sonoran area. The Austroriparian zone comprises the Atlantic coastal plain from Virginia to Georgia and nearly all the Gulf States as far west as the mouth of the Rio Grande ; it also extends up the lowlands of the Mississippi valley to southern Illinois. It is the home of the southern fox squirrel, cotton rat, wood rat, mocking-bird, painted bunting, red-cockaded woodpecker, chuck-will's-widow, and the swallow-tailed kite. A southern portion of this zone, comprising a narrow strip along the coast from South Carolina to Florida and Texas, is semi-tropical, and is the northernmost habitation of several small mammals, the alligator, the ground dove and the Florida screech owl.
The Lower Sonoran zone comprises the most arid parts of the United States : south-western Texas, south-western Arizona and a portion of northern Arizona, southern Nevada and a large part of southern California. Among its characteristic mammals and birds are the desert fox, kangaroo rats, road-runner, cactus wren, hooded oriole and Gambel's quail. It is the northernmost home of the armadillo, ocelot and jaguar. There is some resemblance to the Tropical life-zone at the south-eastern extremity of Texas, but this zone in the U.S. is properly restricted to southern Florida. The area in Florida is small, but it has the true crocodile and is the home of a few tropical birds, including the sooty and noddy terns, great white heron and white-crowned pigeon.