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The Wildlife Health Program of the Wisconsin Department of Natural Resources has moni- tored lead (Pb) exposure in numerous avian species including Bald Eagles (Haliaeetus leucocephalus), Trumpeter Swans (Cygnus buccinator), Common Loons (Gavia immer), and American Woodcock (Scolo- pax minor). A comprehensive review of Trumpeter Swan health data indicated approximately 25% of Trumpeter Swan fatalities were attributed to lead toxicity. Similarly, approximately 15% of live-sampled Trumpeter Swans had blood lead levels above background concentrations (20 µg/dL). A similar review of necropsy data for Bald Eagles revealed approximately 15% of all Bald Eagle deaths in Wisconsin were at- tributed to lead toxicity. A noticeable increase in the percent of fatalities attributed to lead toxicity began in October and peaked in December. This pattern overlapped with the hunting seasons in Wisconsin suggest- ing lead ammunition could be a major source of lead exposure in eagles. A surveillance program examining lead toxicity as a factor in mortality of Common Loons was initiated in 2006. To date, approximately 30% of the dead loons submitted for necropsy were found to be lead poisoned. Lead fishing gear was recovered from the GI tracts of loons in all cases where lead toxicity was a major contributor to the cause of death. A comprehensive study investigating lead levels in woodcock from Wisconsin was completed in 2002. The results of the study indicated American Woodcock were exposed to lead on their breeding grounds in Wis- consin, resulting in high accumulations of lead in bone tissue. Bone lead concentrations considered to be toxic in waterfowl were observed in all age classes of woodcock. Stable isotope analysis was conducted on a subset of bone samples from young-of-year birds in order to identify the source of the lead. The results were inconclusive but did not rule out anthropogenic sources, and although the pathway of lead exposure was not identified, the data suggest a local and dietary source. It is clear that numerous species of Wiscon- sin wildlife are being exposed to potentially harmful levels of lead, and lead poisoning remains a significant mortality factor for many of these species. The prevalence of lead poisoning cases in Wisconsin is unlikely to decrease until the amount of lead discharged into the Wisconsin environment is reduced. Received 9 July 2008, accepted 3 September 2008. STROM, S. M., J. A. LANGENBERG, N. K. BUSINGA, AND J. K. BATTEN. 2009. Lead exposure in Wisconsin birds. In R. T. Watson, M. Fuller, M. Pokras, and W. G. Hunt (Eds.). Ingestion of Lead from Spent Ammu- nition: Implications for Wildlife and Humans. The Peregrine Fund, Boise, Idaho, USA. DOI 10.4080/ilsa.2009.0205 |
