Bird Checklists of the United States Bird Checklists of the United States Agassiz National Wildlife Refuge Middle River, Minnesota Mammals Agassiz National Wildlife Refuge, established in 1937, occupies part of the eastern bed of glacial Lake Agassiz in northwestern Minnesota. This aspen parkland area is located between the coniferous forest to the east. Open water and freshwater marshes occupy 40,000 acres of the refuge, Extensive areas of willow, trees and grasses are found on an additional 21,500 acres on higher ground.
Common trees growing in the hardwood forest are aspen, bur oak, green ash, elm and box elder.
Two black spruce-tamarack bogs with associated bog lakes comprise a 4,000 acre wilderness area. Today there are 74 resident species within the state. Mammals on the refuge range in size form the small pygmy shrew to the large Northwestern moose. Mammals are important in the ecology of the refuge. Herbivores such as mice, squirrels, rabbits, hares, muskrats and deer change plant food energy into animal protein which then becomes available to predators such as mink, gray wolf, hawks and owls.