Twenty-one moist soil units totaling 800 acres are managed to produce food for migrating waterfowl, rails, and shorebirds. Moist soil units are former farm fields developed to impound water through construction of dikes and water control structures. Moist soil management entails manipulating water levels to encourage growth of plants occurring naturally in the seed bank. The plants produce seeds that are high energy food for migrating waterfowl.
Flooding of the moist soil units typically begin in October or November, depending on migration, and proceeds in stages. Initially, one-third of each unit is flooded. Once waterfowl deplete the food supply an additional one-third is flooded, and finally the units are entirely flooded. Progressive flooding concentrates feeding waterfowl to fully utilize moist soil foods. From February through April, waterfowl feed on invertebrates found in the units.
Drawdowns of moist soil units begin in stages to expose mud flats to attract migrating shorebirds which feed on the available invertebrates. The timing of drawdowns also affects the germination of desirable moist soil vegetation to produce food for the following year.
Moist soil units are maintained to limit tree encroachment and other undesirable plant growth. These areas are managed by periodic farming, mowing, disking, herbicides, and water level manipulation.