Widespread Lead Exposure in Golden Eagles Captured in Montana

Lead poisoning threatens many species of raptors, including golden eagles (Aquila chrysaetos). Much of this lead likely comes from bullet fragments that remain in the carcasses of animals killed by hunters. The likelihood of lead exposure may peak during fall hunting seasons and early winter until carcasses from hunting become scarce. From 2011 to 2018 in western Montana, USA, we captured 91 golden eagles in winter, tested their blood lead levels (BLL), and outfitted a subset of birds (n = 29) with global positioning system [GPS] transmitters. Nearly all golden eagles (94.5%) had elevated BLL (>= 10 mu g/dL), and 8 of them had BLL above clinical exposure (>60 mu g/dL), where they may lose coordination and experience a host of other neurological and physiological disorders. Golden eagles caught late in winter tended to have lower BLL than those caught earlier. At least 69% of the golden eagles equipped with GPS transmitters migrated northward, spending the summer throughout Alaska, USA, and northwestern Canada. Blood lead levels did not differ between migratory and nonmigratory golden eagles. Overall, elevated BLL are widespread among golden eagles throughout winter in western Montana. Promoting nonlead hunting ammunition in areas with high densities of golden eagles will reduce the birds' lead exposure. (c) 2020 The Wildlife Society.

Automated summary

Lead poisoning poses a threat to many species of raptors, including golden eagles, with much of the lead likely originating from bullet fragments in carcasses left by hunters. Elevated blood lead levels were found in nearly all golden eagles captured in western Montana during winter, with potential risks including neurological and physiological disorders. Migration patterns did not significantly affect lead exposure levels in these birds. Promoting nonlead hunting ammunition could help reduce lead exposure in areas with high concentrations of golden eagles.