Lead and Mercury in Fall Migrant Golden Eagles from Western North America
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Lead exposure from ingestion of bullet fragments is a serious environmental hazard to eagles. We determined blood lead levels (BLL) in 178 golden eagles (Aquila chrysaetos) captured during fall migration along a major North American flyway. These eagles spent the breeding season distributed over a large range and are the best currently available representation of free flying golden eagles on the continent. We found 58 % of these eagles containing increased BLL > 0.1 mg/L; 10 % were clinically lead poisoned with BLL > 0.6 mg/L; and 4 % were lethally exposed with BLL > 1.2 mg/L. No statistical difference in BLL existed between golden and bald eagles (Haliaeetus leucocephalus). Golden eagles captured on carrion had higher BLL than those captured using live bait suggesting differences in feeding habits among individuals. Median BLL increased with age class. We propose a conceptual model for the long-term increase in BLL after ingestion of lead particles. The mean blood mercury level in golden eagles was 0.023 mg/L. We evaluate a field test for BLL that is based on anodic stripping voltammetry. This cost-effective and immediate method correlated well with results from inductively coupled plasma–mass spectrometry, although results needed to be corrected for each calibration of the test kit.
KeywordsInductively Couple Plasma Lead Exposure Total Mercury Blood Lead Level Mercury Level
We thank the many people who helped in the field, notably A. Shreading, B. Bedrosian, T. Pitz, R. Crandall, S. Wilson, S. Norton, and T. Veto. Kate Davis kindly allowed us to collect blood samples from captive eagles at Raptors of the Rockies. Logistical support was provided by Montana Fish, Wildlife and Parks, United States Forest Service and Helena National Forest (P. Shanley). This work was funded by the Montana Bureau of Land Management, LCAO Foundation, M. J. Murdock Foundation, Maki Foundation, Mountaineers Foundation, Patagonia Foundation, Cinnabar Foundation, and private individuals. K. McKalip provided helpful comments on this manuscript. This work would not have been possible without support from the University of Montana Geosciences Department–Environmental Biogeochemistry Laboratory where all laboratory analyses were performed. Special thanks go to M. Young for help in the laboratory. We thank the two anonymous reviewers for their constructive criticism and suggestions.
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