Exposure of migrant bald eagles to lead in prairie Canada

The prevalence of elevated exposure to lead was assessed in a migrant popul ation of bald eagles (Haliaeetus leucocephalus) at a waterfowl staging area in the southern portion of the Canadian prairies, from September to Novemb er, 1992-1995. Of 103 eagles, 8% exhibited blood lead (PbB) concentrations suggestive of elevated exposure to lead (greater than or equal to0.200 mug ml(-1) wet wt.). PbB concentrations in eagles from the study area ranged fr om < 0.01 to 0.585 <mu>g ml(-1), while those of nestling eagles from a refe rence site indicated normal or background exposure ( < 0.01 <mu>g ml(-1)). No differences in the prevalence of elevated exposure were detected among g enders or age classes (0.5- and greater than or equal to 1.5-year-old birds ) (P > 0.05). The prevalence of elevated exposure was significantly greater in November than in October (21.7 vs. 3.8%) (all years chi (2)(y) = 5.75, p = 0.017). Eagles with shotshell pellets in the digestive tract did not ha ve accompanying high PbB concentrations. The prevalence of elevated lead ex posure in this study was low in comparison to other areas in North America. Potential biases in the trapping technique as they relate to interpreting the results are addressed. (C) 2001 Elsevier Science Ltd. All rights reserv ed.