Theresa Marsh Wildlife Area

History

A glacial lake with a southern outflow once occupied the marsh. Subsequent glacial activity created the present outlet of the marsh flowing to the west and resulted in a vast tamarack and lowland hardwood forest that was logged during settlement times, leaving open marshland. Over the years various agricultural enterprises were attempted in drained portions of the marsh including cattle ranching, canarygrass seed production, muck farming and mint farming, which ultimately failed due to short growing seasons and flooding. The Wisconsin Conservation Commission approved the acquisition of the Theresa Wildlife Area in 1948, and by the late 1960s, nearly 5,000 acres had been purchased. In 1968, a dam was constructed on the East Branch Rock River to allow water level control over hundreds of acres for waterfowl management. In subsequent years several sub-impoundments were constructed across the wildlife area to improve brood-rearing and stopover wetland habitat for waterfowl, and uplands were planted to grassland to provide nesting cover for mallard and blue-winged teal.

Habitat and Wildlife Management

Theresa Marsh is managed for wildlife production, as a migration stopover area for waterfowl and other birds, and to provide a variety of recreational opportunities including hunting, trapping, fishing, bird watching, and hiking.

Water levels at Theresa Marsh are managed to provide diverse wetland habitats, primarily emergent and deep-water marsh. Beginning in spring, some wetland impoundments are dewatered to expose mudflats provide shallow water for migrating shorebirds and allow germination of wetland plants. Wetland annual plants produce large, energy-rich seeds and attract an abundance of invertebrates. These stopover wetlands are reflooded in fall to make these food sources available to migrating waterfowl. In other wetland impoundments water is retained throughout the year to provide brood-rearing habitat for mallards, blue-winged teal, wood ducks, and Canada geese and a nesting habitat for black terns. Periodically, prescribed fire is used in the marsh to manage invasive cattails and encroaching shrubs, increase plant diversity, and allow wetland annuals to germinate. Two waterfowl refuges provide food and resting areas for waterfowl.

Upland grasslands are dominated by tall grass prairie. Grasslands are managed using periodic fire, mowing, and haying to provide nesting cover for mallard, blue-winged teal, and wild turkey and cover and forage for white-tailed deer, wild turkey, and ring-necked pheasants. Pheasants are stocked in upland grasslands throughout the pheasant hunting season.

Farmed fields of corn, hay, soybeans, winter wheat, and other crops provide forage and cover for a variety of wildlife species. Additionally, farming is used to prepare sites for conversion to prairie or forest.