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Effects of methylmercury on reproduction in American kestrels

Authors

  • Peter H. Albers,

    Corresponding author
    1. U.S. Geological Survey Patuxent Wildlife Research Center, Beltsville Lab, % Beltsville Agricultural Research Center-East, Building 308, 10300 Baltimore Avenue, Beltsville, Maryland 20705
    • U.S. Geological Survey Patuxent Wildlife Research Center, Beltsville Lab, % Beltsville Agricultural Research Center-East, Building 308, 10300 Baltimore Avenue, Beltsville, Maryland 20705
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  • Michael T. Koterba,

    1. U.S. Geological Survey Maryland Science Center, 8987 Yellow Brick Road, Baltimore, Maryland 21237
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  • Ronald Rossmann,

    1. U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Large Lakes and Rivers Forecasting Research Branch, Large Lakes Research Station, 9311 Groh Road, Grosse Ile, Michigan 48138
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  • William A. Link,

    1. U.S. Geological Survey Patuxent Wildlife Research Center, Gabrielson Laboratory, 12100 Beech Forest Road, Laurel, Maryland 20708
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  • John B. French,

    1. U.S. Geological Survey Patuxent Wildlife Research Center, Beltsville Lab, % Beltsville Agricultural Research Center-East, Building 308, 10300 Baltimore Avenue, Beltsville, Maryland 20705
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  • Richard S. Bennett,

    1. U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, 6201 Congdon Boulevard, Duluth, Minnesota 55804
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  • Wayne C. Bauer

    1. U.S. Geological Survey Patuxent Wildlife Research Center, Gabrielson Laboratory, 12100 Beech Forest Road, Laurel, Maryland 20708
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Abstract

Sixty breeding pairs of captive American kestrels (Falco sparverius) were exposed to a range of sublethal dietary concentrations of mercury (Hg), in the form of methylmercuric chloride, and their subsequent reproduction was measured. Egg production, incubation performance, and the number and percent of eggs hatched decreased markedly between 3.3 and 4.6 mg/kg dry weight of Hg (1.2 and 1.7 mg/kg wet wt), in the diet. The number of fledglings and the percent of nestlings fledged were reduced markedly at 0.7 mg/kg dry weight (0.3 mg/kg wet wt) and declined further between 2 and 3.3 mg/kg dry weight (0.7 and 1.2 mg/kg wet wt). Dietary concentrations of ⩾4.6 mg/kg dry weight (1.7 mg/kg wet wt) were associated with total fledging failure. The estimated decline in fledged young per pair (24%, Bayesian regression) for kestrels consuming 0.7 mg/kg dry weight (0.3 mg/kg wet wt) raises concerns about population maintenance in areas subject to high inputs of anthropogenic Hg. Mercury concentrations in 20 second-laid eggs collected from all groups were related to dietary concentrations of Hg, and the Hg concentrations in 19 of these eggs were related to eggs laid and young fledged. Concentrations of Hg in eggs from the highest diet group (5.9 mg/kg dry wt; 2.2 mg/kg wet wt) were higher than egg concentrations reported for either wild birds or for captive birds (nonraptors) fed dry commercial food containing 5 mg/kg methylmercury. Accumulation ratios of Hg from diets to eggs were higher than those reported for feeding studies with other species.

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