PATTERNS OF RADIOCESIUM CONTAMINATION IN EGGS OF FREE-RANGING WOOD DUCKS

Studies of biological consequences of nuclear industrial contaminants in the environment increase in importance as the potential for exposur e of wildlife populations rises. Thus, we examined levels of radiocesi um (cesium-137) contamination in wood duck (Aix sponsa) eggs from a De partment of Energy nuclear facility in South Carolina during 1990. Rad iocesium levels in individual eggs from 5 locations on the site ranged from below detectable concentrations (<0.147 Bq/g) to a maximum of 2. 21 Bq/g wet mass. Eggs from an abandoned reactor cooling reservoir con tained the greatest burdens; mean egg concentrations there were more t han an order of magnitude higher than those from other locations studi ed. Eggs from a second abandoned cooling reservoir, Carolina Bays, and 2 lotic ecosystems, one of which had received reactor effluent radion uclide releases, all contained similar low radiocesium levels that wer e, on average, below detection limits. Variation in radiocesium concen trations of eggs from the most contaminated cooling reservoir was part itioned into within- and among-clutch variation. Approximately 33% of the variation in radiocesium content occurred among eggs laid by the s ame female, and may have resulted because females fed in both contamin ated and uncontaminated habitats during egg formation. Radiation dose rates to developing wood duck embryos, resulting from internal and ext ernal sources examined in this study, were below those expected to aff ect hatchability or any other aspect of the breeding biology of these birds. Wood ducks and their eggs may be useful as bioindicators of rad iocesium uptake, but we caution that local foraging patterns could cau se variation in contaminant deposition within clutches.