Avian scavengers, including golden eagles, often eat animals culled though recreational hunting and pest shooting on agricultural lands.
This can provide valuable nutritional subsidies supporting golden eagle populations, but can also expose eagles to harmful amounts of lead from the use of lead-based ammunition. Researchers examined 258 golden eagle chicks in agricultural lands in California, Idaho, Oregon, and Wyoming to determine the benefits and competing impacts of lead exposure around agricultural areas. Although most chicks’ lead concentrations were relatively low, 26 percent contained lead concentrations associated with subclinical poisoning for sensitive species. Eagle chicks living closest to agriculture exhibited the highest growth rates, but also the highest lead concentrations, presumably from eating animals shot with lead-based ammunition. Physiological evidence suggested that lead-exposed chicks had impaired deltaaminolevulinic acid dehydratase activity and may have been anemic and experiencing cellular damage. Stable lead isotope ratios in 89 percent of birds with the highest lead exposure was consistent with those of ammunition. An improved understanding of how positive and negative effects of increased prey availability that may also be lead-contaminated can help managers evaluate broader demographic impacts to golden eagle populations.
Herring, G., Eagles-Smith, C.A., Buck, J.A., Shiel, A.E., Vennum, C.R., Emery, C.S., Johnson, B.L., Leal, D., Heath, J.A., Dudek, B.M., Preston, C.R., Woodbridge, B., 2019, The lead (Pb) lining of agriculture-related subsidies- enhanced Golden Eagle growth rates tempered by Pb exposure: Ecosphere, v. 11, no. 1, p. e03006, https://doi.org/10.1002/ecs2.3006