Foods used by male mallards wintering in southeastern Missouri

Although winter foods of mallards (Anas platyrhynchos) have been documented in several studies, the importance of ecological or biological factors on the consumption of specific food groups often was ignored. Consequently, we evaluated whether age, pair status, molt status, habitat, year, or season influenced foods consumed by male mallards in southeastern Missouri during winters 1983-86. Seeds of moist-soil plants composed 61.4 and 46.0% of the aggregate dry mass diet of ducks collected in 1983-84 and 1984-85. Agricultural grain made up 33.8% of the aggregate dry mass diet in 1984-85, and acorns accounted for 54.5% of the diet in 1985-86. Our analysis revealed that habitat where birds were collected (P < 0.01) and annual variation (P < 0.01) were predominate factors influencing male mallard diet during winter. We attribute annual differences in food consumption primarily to annual variation in mast production. Invertebrates were present in 82% of 156 food samples, but composed only 7.3% dry mass of all ducks collected. Invertebrate consumption was greater during mid-winter than during other portions of winter (P < 0.01), probably a result of population growth and life history strategies of invertebrate species. Consumption of food groups did not differ among adult and immature males (P = 0.75), paired and unpaired males (P = 0.15), or males of different molt status (P = 0.22). These results suggest that age and physiological factors are less important than environmental factors in determining food use by male mallards during winter. Providing a diversity of habitats and suitable foods may be the best management approach to compensate for annual variation in availability of individual food resources.