Managing Wetland Vegetation for Marsh Birds and Waterfowl at Carlyle Lake Wildlife Management Area, IL

The high cost of restoring and managing wetlands warrants careful assessment of their management potential. We designed this study to provide basic information on how seed banks and hydroperiod influence the development of habitat for migratory birds in restored wetlands at Carlyle Lake Wildlife Management Area (CLWMA). The objectives were to: (1) survey the composition of the seed banks; (2) investigate the effects of early- vs. late-drawdowns on the germination and growth of these plants; and (3) monitor the use of these communities by wetland birds during migration and the breeding season. The study was conducted on a marsh complex that included 4 experimental moist soil units. Initially, 2 units were drained in late spring and 2 in early summer; this pattern was reversed during the second year of the study. Seed densities were high in the 4 units, ranging from 14,140 to 21,648 seeds/m2. Native food plants that are important to wetland birds for food sources, cover, and nesting habitat were all abundant. The timing of drawdowns greatly influenced the composition and growth of wetland vegetation in both years. In the first year, Units drained early were dominated by rice cut-grass, beggar-ticks, and smartweeds. Late-drawdowns favored water primrose and water hemp. In the second year heavy rains throughout the summer caused our drawdowns to be completed later than planned. However, vegetation structure of the impoundments still varied with respect to drawdown timing. Early-drawdowns were favored by water primrose, water plantain, sedges, and smartweeds. Duckweeds, pondweeds, and rice cut-grass all dominated the late-drawdowns. Early-drawdowns supported the majority of birds during fall migration, particularly dabbling ducks. But, this trend reversed during spring migration when late-drawdowns were more heavily used. Least bitterns and pied-billed grebes were confirmed nesters at the study areas. Several other state threatened or endangered species were also present at the site throughout their known breeding seasons, however, their nesting was never confirmed. We recommend that CLWMA be managed as a wetland complex by varying the drawdown dates in individual units to provide an array of successional stages, plant communities, and vegetative structures for avian species with diverse habitat requirements. We also recommend that more of the CLWMA be managed for moist soil plant production