DDE, PCB, and mercury residues in Minnesota Common Goldeneye and Hooded Merganser eggs, 1981

Abstract

DDT and its metabolites, polychlorinated biphenyls (PCBs), and mercury (Hg) were measured in Hooded Merganser (Lophodytes cucullatus) and Common Goldeneye (Bucephala clangula) eggs after dead hens were found on clutches. DDE, PCBs, and Hg were detected in all eggs analyzed. Geometric mean concentrations of DDE were low in merganser and goldeneye eggs (0.62 and 0.52 ppm wet weight, respectively). Geometric mean PCB levels were also low, but were significantly higher (P < 0.01) in goldeneye eggs (1.52 vs. 0.66 ppm wet weight). Geometric mean Hg in merganser eggs approached a level for concern and was significantly greater (P < 0.01) than in goldeneye eggs (0.45 vs. 0.11 ppm wet weight, respectively). Merganser and goldeneye eggshells were 9.6 and 15.4% thinner, respectively, and their Ratcliffe indices were 6.0 and 9.2% lower, respectively, than measurements from eggs collected before DDT was in use. Residues and shell thicknesses had among- and within-nest variance structures that differed by species. DDE accounted for 21% of the variation in shell weight controlled for egg size in goldeneyes, but no relationship was evident for mergansers. No dead females were found in about 240 nest boxes monitored in 1982 and 1983 and it is unlikely that contaminant levels measured contributed to hen mortality. Egg breakage in successful nests was greater for goldeneyes than for mergansers or Wood Ducks (Aix sponsa).