Invertebrate community stucture in relation to the foraging ecology of mallard and bufflehead ducklings in western Canada

Aquatic invertebrates are an integral part of wetland function and are essential for duckling growth and development. The western boreal forest (WBF) is the primary breeding ground for Bufflehead ducks (Bucephala albeola ) and supports more than one quarter of the Canadian breeding Mallard (Anas platyrhynchos) population. Understanding invertebrate community ecology and how ducklings use this food source within the WBF are important as this area faces ongoing anthropogenic alteration. Furthermore, there are continental population implications as boreal wetlands can act as alternate breeding habitat for waterfowl during drought years in southern locales.; Aquatic vegetation complexity and prevalence, and fish presence were used to predict the distribution of invertebrate biomass in 24 wetlands within the southern portion of the WBF. Brook Stickleback (Culaea inconstans ) significantly reduced overall invertebrate biomass and the biomass of most functional feeding groups of invertebrates, suggesting a competitive relationship with ducklings. The biomass/L of most invertebrate feeding groups was negatively correlated with dissected-leaf plant dominance, such as Northern Watermilfoil (Myriophyllum exalbescens); presence of this plant has been associated with anthropogenic influence.; Comparative dietary and stable isotope analysis showed that Bufflehead ducklings from the WBF significantly preferred predaceous aquatic invertebrates as prey, specifically the larval form of the predaceous diving beetle (Coleoptera: Dytiscidae). Mallard duckling stable isotope signatures and dietary constituents were compared to the stable isotope signatures and availability of invertebrate prey over three ecozones: boreal plain, aspen parkland, and prairie. Overall, Mallard ducklings also preferred predaceous invertebrates (specifically Coleoptera) and maintained a more constricted foraging niche in boreal habitats, suggesting that the WBF provides more available resources for foraging ducklings than the other two ecoregions. Boreal wetlands also had the highest invertebrate biomass/L. Food limitation can structure waterfowl populations; therefore the food preferences outlined here may help managers understand wetland characteristics important for the sustainability of ducks in the WBF and in other regions.