Wood ducks (Aix sponsa) nesting along Bayou Meto downstream from a hazardous waste site in central Arkansas were contaminated with polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Residues in eggs, based on 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ), ranged up to 611 parts per trillion (ppt), and egg arithmetic means were 90-fold higher at the site nearest the point source compared with a reference site. We monitored productivity of wood ducks in artificial nest boxes at three sites on the bayou and at a reference site on a separate drainage during 1988-1990. Productivity was suppressed (p < 0.05) at the bayou sites compared with the reference site, and egg TCDD-EQs were inversely correlated (p < 0.001) with productivity in corresponding nests. The threshold range of toxicity, where reduced productivity was evident in wood ducks (based on TCDD-EQs), was > 20 to 50 ppt. Oxidative stress and teratogenic effects occurred in ducklings at the more contaminated nesting sites nearest the point source. These findings suggest that wood ducks may be more sensitive to PCDD and PCDF contamination than some other aquatic birds and could serve as an indicator species for monitoring biological impacts from these contaminants.
