Primary foods of American black ducks (Anas rubripes) and mallards (A. platyrhynchos) wintering at Tennessee National Wildlife Refuge were compared by examining esophageal and proventricular contents of ducks collected during winter, 1990-91 and 1991-92. Seeds of natural plants comprised the primary component of the diet of both species. Nodding smartweed {Polygonum lapathifolium), wild millet (Echinochloa crusgalli), lovegrass (Eragrostis hypnoides), and rice cutgrass (Leersia oryzoides) were the most common seeds consumed by both species. Water smartweed (P. hydropiperoides) also was consumed abundantly by black ducks. Black duck samples contained more (P < 0.021) stem and leaf material than mallard samples during both winters and less (P < 0.002) agricultural grain during 1991-92. No differences were detected in food consumption between females and males of either species. Species specific differences in food consumption were probably related to differences in areas from which ducks were collected and perhaps reflected microhabitat differences between species.
