Current risk assessments and wildlife criteria are based on a multi-generational study with mallards, which consume primarily seeds, aquatic vegetation, and some invertebrates. Kestrels were chosen as a surrogate for fish eating birds. They do not normally consume fish; however, they are a raptor and will hopefully behave similar to other raptors. There are few captive populations of birds with enough numbers to permit a risk assessment study. The Kestrel Project provides data that document biotic effects, including reproduction, resulting from known mercury exposures. In support of the project, the LLRS total mercury and methyl mercury laboratories provided analyses of kestrel breast muscle, feathers, blood, brain, liver, and kidney for birds that were dosed with varying amounts of methyl mercury by researchers at the USGS Patuxent Laboratory.
American kestrels (Falco sparverius) were fed meat diets containing 0, 3, 6, or 12 ppm (dry wt.) methylmercury chloride. Birds fed the 12 ppm diet started to show signs of neurotoxicity after 26 days and all died in 39 to 49 days. One male kestrel fed the 6 ppm diet died after 75 days of exposure and several others showed signs of neurotoxicity after 45 days. None of the birds fed the 3 ppm diet died or showed signs of toxicity. After 59 days of exposure, mercury concentrations in liver, kidney, and blood of non-reproducing kestrels increased with increasing dietary concentration. Tissue concentrations of mercury also steadily increased over time in birds fed diets with 6 ppm mercury, which were necropsied at 8, 15, 29, or 59 days of exposure, reaching mean total mercury concentration of 57, 46, and 45 ppm (wet wt.) at 59 days in liver, kidney, and whole blood, respectively. Two pairs of kestrels at each dietary concentration were allowed to breed. Eggs averaged 8.3 and 18.1 ppm (wet wt. ) total mercury from birds fed 3 and 6 ppm diets, respectively. Feathers grown during mercury exposure contained high concentrations of mercury: birds 3 and 6 ppm diets contained 275 and 542 ppm total mercury, respectively. Kestrels appear to be somewhat more sensitive to mercury toxicity than other raptors.
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.
Bennett, R. S., J. B. French Jr., R. Rossmann, and R. Haebler. 2009. Dietary toxicity and tissue accumulation of methylmercury in American kestrels. Arch. Environ. Contam. Toxicol. 56(1):149-156.
Albers, P. H., M. T. Koterba, R. Rossmann, W. A. Link, J. B. French, R. S. Bennett, and W. C. Bauer. 2007. Effects of methyl mercury on reproduction in American kestrels. Environmental Toxicology and Chemistry 26(9):1856-1866.
Rossmann, R. and J. C. Filkins. 2005. Standard Operating Procedure for Analysis of Tissue Samples for Methyl Mercury. LLRS-MET-SOP-021, Revision 3, Large Lakes Research Station, United States Environmental Protection Agency, 16 pp.
Parada, L., M. Levine, and R. Rossmann. 2002. Standard Operating Procedure for Analysis of Samples for the Extraction of Total Mercury in Blood and Feather Samples. LLRS-MET-SOP-023, Revision 0, Large Lakes Research Station, United States Environmental Protection Agency.
Parada, L., M. Levine, and R. Rossmann. 2002. Standard Operating Procedure for Analysis of Samples for Total Mercury using the Milestone Analyzer. LLRS-MET-SOP-022, Revision 1, Large Lakes Research Station, United States Environmental Protection Agency.
Rossmann, R. 2001. Quality Assurance Plan: Methyl Mercury, Total Mercury, and Moisture Content in Kestrel Tissues, Blood, Eggs, and Feces. LLRS-MET-QAP-002, Revision 1, Large Lakes Research Station, United States Environmental Protection Agency.
Filkins, J. C. and R. Rossmann. 2000. Standard Operating Procedure for Preparation of Wet Tissues Prior to Extraction for Total and Methyl Mercury Analyses. LLRS-MET-SOP-019, Revision 1, Large Lakes Research Station, United States Environmental Protection Agency.
Albers, P. H., M. T. Koterba, R. Rossmann, J. B. French, R. S. Bennett, and W. C. Bauer. 2006. Effects of methyl mercury on reproduction in American kestrels. Mercury 2006 Conference on Mercury as a Global Pollutant, Madison, Wisconsin, August 6-11, 2006.
Bennett, R.S., P.H. Albers, M.T. Koterba, R. Rossmann, J.B. French, W.C. Bauer, and K.G. Sappington. 2006. Effects of methylmercury on reproduction in American kestrels and comparison to effects observed in other avian species. SETAC 27th Annual Meeting, Montreal, Quebec, Canada, November 5-9, 2006.
Nichols, J.W., R.S. Bennett, R. Rossmann, J.B. French, and K.G. Sappington. 2006. A combined physiological and bioenergetics-based model for methylmercury in female American kestrels. SETAC 27th Annual Meeting, Montreal, Quebec, Canada, November 5-9, 2006.
Filkins, J. C. and R. Rossmann. 2005. An analytical method for the analysis of methyl mercury in tissue. 48th Conference on Great Lakes Research, International Association for Great Lakes Research, Ann Arbor, Michigan, May 23-27, 2005, p. 55 of abstracts.
Haebler, R., Jr., J. B. French, D. Horowitz, R. Bennett, and R. Rossmann. 2004. Pathological effects of dietary methyl mercury in American kestrel (Falco sparverius). SETAC Annual Meeting, Portland, OR, November 14-18, 2004, p. 4302 of abstracts.
French, J. B., Jr., D. Graham, B. Rattner, D. Hoffman, G. Heinz, R. Bennett, and R. Rossmann, 2001. Dietary methyl mercury exposure in American Kestrels; pilot studies. SETAC 22nd Annual Meeting, Baltimore, Maryland, November 11-15, 2001.
A controlled egg dosing study was done to directly test the effects of in ovo MeHg exposure on chick quality. A USGS and WDNR pilot study was done in 2005, and the full study was done in 2006. The results of these efforts are being used to enhance the Loon Chick Hg Exposure Model under development by the Wisconsin DNR, USGS, and University of Wisconsin to produce a Loon Life Cycle Exposure Model. The model will provide a prediction of common loon Hg exposure levels throughout their lifetime, including loon egg mercury concentrations as a function of adult dietary MeHg intake. A full egg injection study produced additional critical endpoints with which to establish a more rigorous Wildlife Hg Criteria Value. The LLRS Chemistry Laboratories provided analysis of loon muscle, liver, kidney, brain, blood, yolk sac, carcass, egg remnants, and down for total and methyl mercury.
Custer, T. W., C. M. Custer, P. Dummer, K. P. Kenow, M. W. Meyer, and R. Rossmann. 2009. Mercury contamination in tree swallows nesting at northern Wisconsin inland lakes that differ in methylation potential. Midwest Chapter of the Society of Environmental Toxicology and Chemistry Meeting, 30 March – 1 April 2009, La Crosse, Wisconsin.
Kenow, K. P., M. W. Meyer, and R. Rossmann. 2009. Patterns and consequences of in ovo exposure to methylmercury in common loons. Midwest Chapter of the Society of Environmental Toxicology and Chemistry Meeting, 30 March – 1 April 2009, La Crosse, Wisconsin.
Kenow, K. P., M. W. Meyer, and R. Rossmann. 2008. Patterns and consequences of in ovo exposure to methylmercury in common loons. Workshop on Integrating Multimedia Measurements of Mercury in the Great Lakes Region, November 10-12, 2008, La Crosse, Wisconsin.
Kenow, K. P., M. Meyer, and R. Rossmann. 2006. Establishing mercury toxicity thresholds for critical life stages of common loons – in ovo exposure. SETAC 27th Annual Meeting, Montreal, Quebec, Canada, November 5-9, 2006.
Kenow, K. P., M. W. Meyer, and R. Rossmann. 2006. Patterns and consequences of in ovo exposure to methylmercury in common loons. Mercury 2006 Conference on Mercury as a Global Pollutant, Madison, Wisconsin, August 6-11, 2006.