Historically, oak savanna was the predominant habitat on the upland areas that are now part of the refuge. Habitat management includes reestablishment of prairie grasses and wildflowers that once dominated the oak savanna through an active planting program. Big bluestem, little bluestem, Indiangrass and switchgrass, as well as a rich diversity of native prairie wildflowers (forbs) can now be found here. Oak seedlings are being planted in some portions of the refuge to restore the overstory of the oak savanna, while in other areas oaks are naturally spreading into the grassland plantings. Oak savanna is a fire dependent plant community, and is managed at Sherburne with an active prescribed burning program. With restoration of historic habitat, animals of the oak savanna are also returning.
On the refuge, restored wetlands, commonly referred to as impoundments or pools, as well as natural lakes and wetlands, provide homes for many species of wildlife including waterfowl, wading birds, shorebirds, mammals, frogs, turtles, and salamanders. Wetlands are scattered throughout the other two refuge habitats, oak savanna and big woods, in their low lying areas, and comprise about one-third of our acreage. Sherburne has 22 restored wetlands where the water level can be manipulated. These impoundments are managed by controlling the water level. Not all of the impoundments are kept at the same depth. Water management by controlled fluctuations creates a variety of habitats to provide for a diversity of wildlife requirements.
Big Woods, sometimes referred to as a maple-basswood forest, was historically dominated by these two tree species. The understory is comprised of shade tolerant herbaceous (leafy) plants. It is home to animals including deer, black bears, squirrels and many songbirds. Woodlands near the northern boundary of the refuge are managed to preserve native trees and restore the Big Woods habitat. Snags and downed timber are retained for use by wildlife for roosting, loafing, nesting, hunting, feeding and food storage. Occasional prescribed burns are used to reduce woodland fuel buildup, so that if a wildfire occurred, valuable wildlife habitat would not be destroyed.
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Mille Lacs National Wildlife Refuge, which is managed by Sherburne NWR Complex, is the smallest refuge in the NWR system. It also hosts one of only five common tern breeding colonies in Minnesota. This year Mille Lacs NWR is "terning" 100 and you're invited to our centennial celebration on Friday, June 12 from 10 a.m. to 2 p.m. at Father Hennepin State Park.