Relative abundance and population trends are calculated for the entire state but also for 7 ecological regions within the state. These are based on the "ecoregional sections" delimited by McNab and Avers (1994) and Keys et al. (1995), with the additional separation of the "Central Sands" from the remainder of southeastern Wisconsin. For brevity, we call these "regions" and abbreviate their names as follows.
The Northwest Forest region mostly comprises extinct glacial lake beds with sandy or peaty soils and is dominated by pine and oak barrens and woods, some more mesic forest and relatively nonintensive agriculture. This region has numerous lakes, streams, marshes, and bogs.
The large Northcentral Forest region is mostly forested with northern hardwoods, although nonintensive agricultural land is scattered and more intensive agriculture dominates some southern parts. Much of this region is on Precambrian shield overlain by morainal deposits and sandy outwash; lakes and bogs are common.
The Eastern Forest region was formerly dominated by mesic maple, beech and pine forests, with substantial cedar swamps. Large marshes lined the west shore of Green Bay. Forest stands are now concentrated west of Green Bay and are scattered among agricultural fields on the Door County peninsula and southward. Some marshes remain, the largest along the west shore of Green Bay. The area along the Fox River leading into Green Bay is highly industrialized and the southern lobe of the region is densely populated.
The Central Sands represent the bed of extinct Glacial Lake Wisconsin, and associated uplands. This region includes extensive natural and restored marshes, sedge meadows, lowland hardwoods, and conifer bogs, as well as commercial cranberry operations, irrigated cropland and pasture, and large tracts of pine and oak forest, aspen, and pine plantations.
The pre-Euro-American settlement landscape of the Southeast region was primarily oak savanna with some major prairies, oak woodland, and wetland complexes. It is now mostly agricultural with small scattered woodlots and some fairly extensive marshes. Urbanization is spreading from the major metropolitan areas of Milwaukee and Madison.
The hilly Driftless Area, with its characteristic sandstone and dolomite exposures, was missed by the last Pleistocene glaciers. It contains mostly small farms and ridgeside oak and maple woods. Small, wet meadows are occasionally associated with the many spring-fed "coulee" streams. Marshes and lowland hardwoods are concentrated along the Mississippi River floodplain and several large rivers that feed the Mississippi. Pasture is more common here than elsewhere, especially in stream bottoms and in some of the former prairies and oak savannas south of the Wisconsin River.
No routes occur in the St. Croix region, which is mixed agriculture and woodlots, with scattered ponds and marshes.