Aquatic systems in the Midwest have been highly modified since the beginning of the 20th century, including channelization, damming, and dredging of most large rivers (e.g., Illinois, Mississippi, Ohio, Missouri) and disconnection from their natural floodplains with networks of levees. While the loss of submersed aquatic vegetation from hydrologically-connected wetlands and backwater lakes along the Illinois and Mississippi rivers is well-documented, information is unavailable to determine the implications of these losses on energetic carrying capacity for waterfowl, especially dabbling ducks. The objective of this study is to estimate true metabolizable energy of six species of submersed aquatic vegetation common to the Upper Midwest for dabbling ducks. We have conducted feeding trials using wild-caught mallards (Anas platyrhynchos) during autumn 2015 and wild-caught gadwall (Anas strepera) in autumn 2016. Feeding trials consist of a 48−hour fast, precision feeding of focal submersed aquatic vegetation (e.g., Stuckenia pectinata) followed by a 48−hour period in a metabolic chamber to collect excreta. Gross energy of test foods and excreta were determined using a Parr oxygen bomb calorimeter, and were corrected for digestion efficiency to ascertain true metabolizable energy. We expect the true metabolizable energy of submersed aquatic vegetation to be less than that of seeds, tubers, and other hard mast. True metabolizable energy analysis will be completed during autumn 2016 and will be included in the presentation. Our data will be useful to conservation planners for estimating energetic carrying capacities of semi-permanently-flooded marsh habitats, which will aid in projecting impacts of wetland management alternatives (i.e. semi-permanently-flooded marsh versus moist-soil management). Understanding the true metabolizable energy of submersed aquatic vegetation will allow managers to assess the impacts on dabbling ducks of wetland habitat change over time or in response to stressors (e.g., hydrologic connectivity with rivers/lakes, climate change).
|Original language||English (US)|
|Title of host publication||Private Landscapes, Public Responsibilities: 77th Midwest Fish & Wildlife Conference, February 5-7, 2017, Lincoln, Nebraska|
|State||Published - 2017|