The Rush Creek IBA includes the Rush Creek State Natural Area. This site is characterized by some of the most intact forestland (along with adjacent floodplain forest) in Wisconsin?s Driftless Area. The topography of this site is quite steep, with many sections having exposed bedrock. Most south and west-facing slopes are dominated by oaks and hickories, while the north-facing slopes have maples, basswood, and oak. Black walnut and aspen are also present. A floodplain forest of silver maple, hackberry, and swamp white oak also is found here, along with oak savanna. Important non-forest habitats include cool-season grasslands and a set of dry lime prairies located on steep southwest-facing bluffs along the Mississippi River. These dry, rocky prairies are among the most extensive remaining examples of this plant community in the Midwest, saved from the plow by virtue of their steep, rugged aspect. Many rare species of plants and animals occur here including purple milkweed, broad beech fern, hairy meadow-parsnip, Kentucky coffee tree, wing snaggletooth snail, and gorgonne checkerspot butterfly (WDNR 2006).
Rush Creek provides habitat for a range of bird species associated with floodplain forest, upland deciduous forest, oak savanna, and dry prairie. Seven endangered or threatened bird species are found here in significant numbers. The site contains core habitat for the Cerulean Warbler, with as much as 4,000 acres of habitat essential to this species available on this site. Numerous other high conservation priority species also breed here including Red-headed Woodpecker, Brown Thrasher, Yellow-throated Vireo, Blue-winged Warbler, and Louisiana Waterthrush. During migration, thousands of raptors pass through the site, and Bald Eagles congregate here in winter.
Agriculture, timber harvesting, and road and power grid development altered this area in the past. Currently, the area is experiencing increasing pressure for residential development, particularly for blufftop homes. Other threats include unsustainable forest management practices, the spread of invasive species, grazing, and succession, especially for savannas and grasslands. Dry prairies, in particular, are increasingly rare. Many remnants are small, isolated, and difficult to manage, and are vulnerable to loss through fragmentation and succession (WDNR 2005). Intact blocks of forest, savanna, and prairie should be maintained, and managed as a complex of habitats wherever possible. Residential development should be limited to prevent fragmentation and retain the possibility of using fire as a management tool. Private landowners should be encouraged to use sustainable forest management practices and to restore savanna or prairie through partnerships with conservation organizations, land trusts, county and local governments, and other stakeholder groups.