Mid-Winter Food Use and Body Weights of Mallards and Wood Ducks in Mississippi

Abstract

We obtained esophageal food samples from 311 mallards (Anas platyrhynchos) and 94 wood ducks (Aix sponsa) and body weights from 2,118 mallards and 315 wood ducks in western Mississippi during December and January 1979-83. On average, mallards ingested 3.0% animal food, principally aquatic invertebrates, and 97.0% plant food. Rice, soybeans, and seeds of moist soil plants provided 41.3, 41.6, and 10-11% of the total food intake. Wood ducks ingested nearly 100% plant food, of which 23.4% was soybeans and 74.3% was acorns from Nuttall (Quercus nuttallii), water (Q. nigra), and willow oaks (Q. phellos). Mallard food use varied with water conditions; the use of rice decreased and soybeans increased during 1980-81 when cumulative November-January precipitation was 2,500 waterfowl publications and found that only 211 (8%) pertained to winter, 14 (0.5%) concerned the MAV, and still fewer dealt with feeding ecology in the MAV. Although data are available concerning the foods of waterfowl wintering in the Lower Mississippi Valley, most pertain to coastal marshes (Davis et al. 1961, Junca et al. 1962, Glasgow and Bardwell 1965) or encompass broad geo44 DUCK FOODS AND WEIGHTS * Delnicki and Reinecke J. Wildl. Manage. 50(1):1986 graphical areas (McAtee 1918, Martin and Uhler 1939). Wright (1961) and Forsyth (1965) have provided the principal esophageal food habits data for mallards wintering in the MAV. Because mallards forage in agricultural areas more readily than wood ducks, these 2 species can provide valuable comparative data on feeding ecology in bottomland habitats. Accordingly, our study was designed to measure the relative contribution of natural and agricultural foods to the mid-winter diet of mallards and wood ducks and to relate food use to habitat conditions and bird weights. We are grateful to the waterfowl hunters of Mississippi, particularly D. Barrett, P. M. Barrett, Jr., B. J. Cross, and J. C. Griffin, for allowing us to dissect their ducks. F. J. Horne, R. E. Kirk, and G. Simard assisted with fieldwork. H. B. Bell and G. L. Chandler, former managers, and the staff at Hillside Natl. Wildl. Refuge provided use of refuge facilities. C. R. Bingham, A. H. Clarke, L. G. Sanders, and F. M. Uhler aided in taxonomic identifications, and B. K. Williams and E. D. Heinlein supervised the statistical analyses.