Ecological Factors Influencing Waterfowl Production on Three Impoundments in Central Wisconsin

Abstract

Waterfowl productivity and breeding ecology were studied on three publically-owned impoundments in southern Wood County, Wisconsin in 1975 and 1976. Production of near flight-aged young was less than one third of that previously reported for Wisconsin's high production area (Horicon Marsh) in the southeast section of the state. Low waterfowl production is a.product of poor quality habitat on the study areas. Organic soils are acidic, not well decomposed, and have low nutrient contents, except for phosphorus which probably occurs in an unavailable form. Waters are soft, slightly acidic, have low dissolved solid concentrations, and are moderately fertile. Succession is advanced on all study areas and the impoundments do not have sufficient interspersion of emergent vegetation and open water. Surface and benthic aquatic invertebrate populations are comparatively low throughout the breeding season and are probably inadequate to meet the high protein requirements of more breeding hens and developing ducklings. Potential upland nesting habitat is inadequate, particularly for blue-winged teal (Anas discors), on all study areas. Nest predator activity is not excessively high. Duck production is higher on J-Flowage and WC-North, where a generally higher quality habitat prevails, than on WC-South. Water quality is better, plant succession is not as advanced, and invertebrate food sources are greater on these areas than on WC-South. Emergent species composition in WC-South is essentially a spikerush (Eleocharis palustris) monotype; J-Flowage and WC-North contain suitable mixtures. Submergent vegetation is sparse on WC-South; J-Flowage and WC-North have dense stands of coontail (Ceratophyllum demersum) or water weed (Anacharis canadensis). Differences in hydrologic characters of the wetlands account for variation in quality. Habitat management practices are recommended.