Ectoparasite and trichomonosis management improve nestling golden eagle (Aquila chrysaetos) health and survival: An effective mitigation strategy

Management of emerging pathogen and parasite threats could provide cost-effective compensatory mitigation options for protected species, such as golden eagles (Aquila chrysaetos). Golden eagle nestlings are vulnerable to infestations of poultry bugs (Haematosiphon inodorus), a blood-sucking ectoparasite that lives in nest material and trichomonosis, a highly lethal disease caused by the protozoan Trichomonas spp. We aimed to develop effective treatment protocols for poultry bugs and trichomonosis and project whether nestling parasite and disease management would have population-level effects in this long-lived apex predator. We collected pre-treatment data on poultry bug loads in eagle nests; then, we applied 1 of 3 experimental parasite treatments to empty eagle nests in late summer months: a combination of permethrin and diatomaceous earth, diatomaceous earth-only or water—a control, and measured effects on poultry bugs and nestlings the following year. During nestling exams, we treated trichomonosis-infected nestlings with an anti-protozoan drug. Then, we projected the effects of treatments on population growth using simulation models. The permethrin and diatomaceous earth nest treatment significantly reduced poultry bug densities in the subsequent breeding season and improved nestling health and survival. Nestlings had significantly greater haematocrit; female nestlings had greater mass, and, on average, 0.70 more nestlings successfully survived to fledge compared with control- and diatomaceous earth-only-treated nests. Ten eagle nestlings from 27 nests that likely would have died from trichomonosis lived to fledge from the nest after treatment. Over 2 years, we estimate saving 17.5 nestlings, which equates to 10.2 adult eagles. We projected that treatments of poultry bugs and trichomonosis could increase local eagle population growth rates by 8% and 4%, respectively. Synthesis and applications. For sensitive or at-risk bird species, treating parasites and disease can improve nest productivity and support population growth, making it a valuable conservation tool. In areas with high concentrations of poultry bugs or where eagles consume avian vectors of Trichomonas spp., pathogen and parasite treatments may serve as an effective mitigation strategy with population-level benefits for eagles.