The lead (Pb) lining of agriculture‐related subsidies: enhanced Golden Eagle growth rates tempered by Pb exposure

• Published in: Ecosphere
• Main Authors: Herring, Garth, Eagles‐Smith, Collin A., Buck, Jeremy A., Shiel, Alyssa E., Vennum, Chris R., Emery, Colleen, Johnson, Branden, Leal, David, Heath, Julie A., Dudek, Benjamin M., Preston, Charles R., Woodbridge, Brian
• Other Authors: U.S. Fish and Wildlife Service, U.S. Geological Survey, U.S. Bureau of Land Management, National Science Foundation, Boise State University
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2020
• Subjects: Aquila chrysaetos; golden eagle
• Online Access: http://dx.doi.org/10.1002/ecs2.3006; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fecs2.3006; https://onlinelibrary.wiley.com/doi/pdf/10.1002/ecs2.3006; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ecs2.3006; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecs2.3006

Abstract Supplementary food resources (e.g., subsidies) associated with agriculture can benefit wildlife species, increasing predictability and availability of food. Avian scavengers including raptors often utilize subsidies associated with both recreational hunting and pest shooting on agricultural lands. However, these subsidies can contain lead (Pb) fragments if they are culled with Pb‐based ammunition, potentially leading to Pb poisoning and physiological impairment in wildlife. Nesting Golden Eagles ( Aquila chrysaetos ) commonly forage in agricultural lands during the breeding season, and therefore, both adults and their nestlings are susceptible to Pb exposure from scavenging shot wildlife. We assessed drivers of Pb exposure in 258 nestling Golden Eagles (401 total blood samples), along with physiological and growth responses, in agricultural lands across four western states in the United States. We also evaluated the birds’ Pb stable isotope signatures to inform exposure sources. Twenty‐six percent of Golden Eagle nestlings contained Pb concentrations associated with subclinical poisoning for sensitive species (0.03–0.2 μg/g ww), 4% had Pb concentrations that exceeded subclinical poisoning benchmarks (0.2–0.5 μg/g ww), and <1% exceeded either concentrations associated with clinical poisoning (0.5–1.0 μg/g ww) and or those deemed to cause severe clinical poisoning (>1.0 μg/g ww). Lead concentrations were highest in nestlings with close proximity to fields that potentially provided subsidies and declined exponentially as distance to subsidies increased. However, close proximity to agriculture, and presumably subsidies, positively influenced nestling growth rates. Across the range of Pb exposure, nestlings experienced a 67% reduction in delta‐aminolevulinic acid dehydratase (δ‐ALAD) activity, suggesting nestlings may have been anemic or experiencing cellular damage. Isotopic ratios of 206 Pb/ 207 Pb increased non‐linearly with increasing blood Pb in Golden Eagle nestlings, and 45% of the birds were ...