Feces from tundra swans [Cygnus columbianus (Ord)], Canada geese [Branta canadensis (L.)], and mallards [Arias platyrhynchos (L.)] were collected from the Coeur d'Alene River Basin and two reference areas in Idaho to estimate exposure to lead from mining activities and relate that exposure to the ingestion of contaminated sediments. The average acid-insoluble ash content of the feces, a measure of sediment ingestion, was 18% for Canada geese and tundra swans, and 12% for ducks. The 18% value corresponded to an estimated 9% sediment ingestion rate (dry weight). The 90th percentile for acid-insoluble ash in feces of tundra swans corresponded to an estimated 22% sediment in the diet. The average lead concentration (dry weight) of tundra swan feces from all Coeur d'Alene River Basin wetlands sampled was 880 mg/kg, compared to 2.1 mg kg⁻¹ from reference areas. The 90th percentile of lead in tundra swan feces from the Coeur d'Alene River Basin sites was 2700 mg kg⁻¹. Fecal lead concentrations of tundra swans were correlated (Spearman's rho = 0.74, P < 0.05) with the acid-insoluble ash content of the feces. The very low lead concentrations in feces having low acid-insoluble ash contents established that the sediment was the primary source of the lead ingested by waterfowl. Sediment lead concentrations at 11 wetland sites were closely correlated (r = 0.91, P < 0.05) with average fecal lead concentrations for all waterfowl, corrected for the average percent acid-insoluble ash in the feces.