Radiocesium patterns in wood duck eggs and nesting females in a contaminated reservoir

Radionuclide releases from nuclear industry are an important ecological issue, particularly because these contaminants may directly affect animals and may be transferred to the hunting public through consumption. During 1991-92, we collected 13 clutches of wood duck (Air sponsa) eggs from nest boxes established in an abandoned reactor cooling reservoir. We examined whole-egg radiocesium (Cs-137) levels and apportionment within egg components (albumen, yolk, and shell). Whole-egg concentrations averaged 0.113 Becquerels (Bq)/g wet mass (SE = 0.01, n = 137) over 2 years. Albumen had the highest concentration of Cs-137 ((x) over bar = 1.096 Bq/g dry mass), followed by shell ((x) over bar = 0.132 Bq/g dry mass) and yolk ((x) over bar = 0.098 Bq/g dry mass). Levels of potassium (K), a chemical analog of Cs, suggested that contamination levels in yolk were disproportionally lower than those in albumen. Levels of Cs-137 that appeared in these components may reflect temporal differences in the synthesis of yolk and albumen. Laying order did not relate to whole-egg Cs-137 concentrations within clutches, but Cs-137 concentrations in post-laying females were positively related to mean egg Cs-137 levels in their respective clutches (r(2) = 0.97). While female ducks and their eggs examined in this study would not have posed a health hazard to persons consuming them as food, we suggest that Cs-137 levels in breeding female wood ducks and their clutches may be indicators of foraging habitat selection (both contaminated and uncontaminated) during the laying cycle.