Free-ranging waterfowl wintering in and migrating through central Oklahoma were collected and examined for intestinal helminths. Seventy-one ducks, including mallards (Anas platyrhynchos), American widgeons (Anas americana), blue-winged teal (Anas discors), and green-winged teal (Anas crecca) were examined; 64 (90.1%) harbored one or more species of metazoa. Six cestodes, 6 trematodes, 6 nematodes, and 1 acanthocephalan were identified. An experimental, non-flying population of ducks was established and monitored to determine the extent of helminth transmission in central Oklahoma. Seven species of helminths were acquired by the sentinel birds during the study. The significance of the parasites recovered and variations in prevalence and species composition of the infections are discussed as they relate to the life cycles of the parasites and the ecology of the hosts.