Historically, the Big Lake State Park was mosaic of wet prairie, marshland, and bottomland forest within the Missouri River floodplain (Nigh and Schroeder 2002). Big Lake SP contains Missouri’s largest natural oxbow lake, and is one of only a few remaining natural wetlands in the state. The park contains the largest marsh within Missouri’s state park system. Boundaries of the IBA are superimposed on those of Big Lake SP (MDNR).

The IBA provides wetland habitat for breeding, migrating, and wintering waterbirds. Large concentrations of waterfowl and shorebirds frequent the IBA during spring and fall migration, moving between this and other large wetlands in the vicinity. Bald Eagles have attempted nesting adjacent to the area, and Least Bittern, Pied-billed Grebes, Yellow-headed Blackbirds, and other marshbirds regularly breed on the area. American Bittern have also been observed in the vicinity of the IBA during the breeding season (Jacobs and Wilson 1997), and probably breed within the park during some years.

The Missouri Department of Natural Resources is managing wetland habitats on Big Lake SP, in conjunction with heavy public use. A major land acquisition in 1989 helped preserve the remaining marsh habitat. Boaters and jet-skiers may present a disturbance to nesting eagles and other birds on Big Lake.