Reproductive success, environmental contaminants, and trophic status of nesting Bald Eagles in eastern Newfoundland, Canada

Eastern Newfoundland contains a large breeding population of Bald Eagles (Haliaeetus leucocelihalus). Our objectives were to determine the reproductive success, contaminant levels, and trophic statis of Bald Eagles in eastern Newfoundland, and to compare contaminant levels of eagles in industrialized and noninclustrialized coastal bays (Placentia and Bonavista bays, respectively). Bald Eagle breeding density in eastern Newfoundland was 0.09 occupied nests/km shoreline, and reproductive success suggested a healthy population (1.1 young/occupied nest). Geometric mean concentrations of PCBs and DDE in nestling plasma were significantly higher in Placentia Bay (PCBs = 30.0 ng/g [wet wt]; DDE = 9.0 ng/g) than in Bonavista Bay (PCBs - 10.0 ng/g; DDE - 2.0 ng/g). Within Placentia Bay, concentrations of PCBs and DDE in nestlings were negatively related to the nest distance from the former U.S. naval base at Argentia. Geometric mean concentration of mercury in whole blood of eagle nestlings was 87 ng/g (wet wt). Analysis of prey remains collected at nests and of stable-carbon (C-13/ C-12) and nitrogen (N-15/N-14) isotope ratios in nestling blood indicated some differences between nests in food sources, but not in relative trophic level. Prey remains collected at 30 Bald Eagle nests were composed of 64% birds, 29% fish, and 7% mammals. Contaminant burdens in Bald Eagles in eastern Newfoundland were lower than those in populations from more industrialized areas of North America and were below thresholds for reproductive impairment. These results provide all essential baseline for future monitoring of the eagle population as industrial development increases in Placentia Bay.