Dabbling Duck and Aquatic Macroinvertebrate Responses to Manipulated Wetland Habitat

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Abstract
Responses of breeding dabbling ducks (Anatini) and aquatic macroinvertebrates to experimental modifications of cover:water ratio and basin surface were investigated in 1977 and 1978 within an impounded whitetop rivergrass (Scolochloa festucacea) meadow on the Delta Marsh, south-central Manitoba [Canada]. Three areal percentage ratios of emergent hydrophytes to open water (30:70, 50:50 or 70:30) and 2 basin treatments (mowing of existing emergents or scarification by rototilling) were tested. Between years, pair numbers of mallards (Anas platyrhynchos) and blue-winged teal (A. discors) declined; pair numbers of northern shovelers (A. clypeata), gadwalls (A. strepera) and pintails (A. acuta) were comparable. The greatest density and species diversity of dabbling duck pairs occurred on 50:50 plots in both years. Only blue-winged teal and pintail pair densities in 1978 were greater on mowed than on rototilled areas. Within years, species diversity of dabbling ducks was unaffected by moving or rototilling. More pursuit flights arose from 50:50 plots and mowed areas compared to alternative treatments. Composition and resource levels (abundance, biomass and number of families) of aquatic macroinvertebrate communities varied within and between years in response to basin treatments. Prescriptions for wetland habitat management were implied.

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