Acorn selection by female wood ducks

Acorns of southern bottomland red oaks (Quercus spp.) are important winter foods of wood ducks (Aix sponsa). Therefore, we tested if captive, wild-strain female wood ducks would exhibit preferences among different species of common bottomland red oak acorns, including willow oak (Q. phellos), water oak (Q. nigra), cherrybark oak (Q. falcata var. pagodaefolia), and Nuttall oak (Q. nuttallii) during winter 1991-92. Willow oak acorns were selected over all other equally available acorns, whether presented in mixed- or single-species feeding trials. Willow oak acorns had smalles top width, thinnest shell, and greatest meat: shell mass ratio, which perhaps facilitated ingestion and nutrient assimilation by wood ducks. Future research should clarify mechanisms for acorn selection by wood ducks and mallards (Anas platyrhynchos) in captive and natural environments. Managers might use willow oak and other appropriate tree species (i.e., considering geographical, hydrological, and soil conditions) in restoration of lowland hardwood forests.