Moist-soil wetlands that are seasonally flooded provide important habitats for waterfowl in the Mississippi Alluvial Valley (MAV). These wetlands often contain tall and dense vegetation that may constrain waterfowl use before natural openings form. During winters 2006–2009, I estimated abundances of waterbirds, seeds and tubers, and invertebrates in response to autumn, prelooding treatments of light disking, mowing, and no manipulation (control) of vegetation in 26 moist-soil wetlands in the MAV. Seeds and tubers were most abundant in control and mowed plots in late autumn. Decomposition was least and invertebrate abundance was greatest in control plots during winter. Dabbling ducks were most abundant in mowed and disked plots during winter. Lightly disked plots contained ~30% fewer seeds and tubers than mowed and control plots. In late winter, ~260 kg[dry]/ha of seeds and tubers remained among mowed, disked, and control plots. Therefore, autumn mowing of robust moist-soil vegetation can be used to create an interspersion of emergent vegetation and open water attractive to waterfowl and conserve waterfowl foods. Additionally, I identified 6 seed taxa that may not be used for food by dabbling ducks (i.e., Amaranthus spp., Cyperus odoratus, Eleocharis spp., Ipomoea spp., Jacquemontia tamnifolia, Sesbania herbacea) and estimated that removing these and other taxa not reported in diet literature in the MAV resulted in a ~31% reduction in estimated moist-soil food availability for ducks. In other experiments, I estimated that waterfowl reduced experimentally placed Japanese millet (Echinochloa frumentacea) to ~10 kg/ha and other natural seeds and tubers to ~170 kg/ha in experimental plots in mid-winter. However, waterfowl did not abandon wetlands or stop foraging when seed reduction ceased, suggesting residual abundances of seeds and tubers represented a food availability threshold (FAT). Using the median FAT value of 220 kg/ha from both experiments and removing 31% of seed mass that may not be consumed by dabbling ducks, results in a ~70% decrease in moist-soil seed availability in the MAV. Conservation planners should consider reducing the current estimates of seed and tuber availability and recommend increasing active management or implementation of additional managed, moist-soil wetlands in the MAV.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-6025 |
| Date | 10 December 2010 |
| Creators | Hagy, Heath Michael |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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