This is the largest RWB marsh at 1989 acres (1163 wetland marsh acres and 826 upland acres) and perhaps the best. It is one of the few basins with permanent water and has some of the best marsh vegetation. During spring it hosts hundreds of thousands of geese (especially greater white-fronted), and some 20 species of ducks. Thousands of shorebirds use this site from March through May and again in early fall. In April and October, whooping cranes have used this area. From May through September you might see cattle egrets, black-crowned night herons, great blue herons and great egrets. White-faced ibis and cinnamon teal are regularly seen here. Pelicans, double-crested cormorants, and eared grebes are common in the deeper water areas. Birds that nest here include great-tailed grackles, yellow-headed blackbirds, eared and pied-billed grebes, least bitterns, Virginia rails, northern harriers and common yellowthroats. Playing birdsong tapes of sora and Virginia rails should elicit a response.
The amount of surface water present each spring greatly affects waterfowl usage and natural runoff may be supplemented by groundwater pumping when needed. Funk lagoon includes large areas of open water, moist soil wetlands and restored native grasslands. Hiking trails along dikes offer excellent opportunities to view wildlife any time of the year. A three-mile loop trail begins and ends at the main parking lot which has an information kiosk with maps and a nearby handicap-accessible observation blind that looks out over the marsh. The wetland is the collecting area for runoff from a large watershed. It can quickly go from nearly dry to flooded, after a heavy summer rain. Recent management has included prescribed burning, grazing, silt removal, disking, and reseeding of native grasslands. Dry conditions have allowed aggressive management of the areas choked with cattail and reed canarygrass.