Big Oaks Refuge contains the largest unfragmented forested block in southeastern Indiana and some of the largest grassland areas found within the region. The refuge provides habitat for 120 species of breeding birds, the Federally endangered Indiana bat, and 41 species of fish. The refuge also is home to white-tailed deer, wild turkey, river otters, and coyotes. Over 25 State-listed animal species and over 46 State-listed plant species have been discovered to date on the refuge. Many bird species of management concern are also found here, including Henslow’s sparrows and cerulean warblers. Over 800 singing male Henslow’s sparrows use the large grasslands on the refuge. Big Oaks National Wildlife Refuge has been designated as a Globally Important Bird Area because of its value to Henslow’s sparrows and other migratory birds.