One-Time treatment of nest material is enough to prefent parasitism by Philornis pici in the endemic and critically endangered Ridgway’s Hawk (Buteo ridgwayi) on Hispaniola

QUIROGA, M.; HAYES, T.; HAYES, C.

Boise

Conferencia; Raptor Research Foundation and the Neotropical Raptor Network Annual Conference; 2021

The Peregrine Fund

Parasitic flies of the genus Philornis cause fitness costs to their avian hosts, especially in geographically-restricted and endangered bird species. This group of Neotropical ectoparasites affects a wide array of avian hosts, including raptors. Ridgway’s Hawk is a Critically Endangered species endemic to Hispaniola. A high percentage of Ridgway’s Hawk nestlings die due to parasitism by subcutaneous-feeding larvae of Philornis spp. (primarily P. pici). The Peregrine Fund began experimental treatments of Ridgway’s Hawk nests in 2012, by 2013 we had developed a highly effective treatment to prevent Philornis-related death in nestling hawks. However, this treatment was not ideal since it was costly and time-consuming, directly exposed nestlings to insecticide (applied topically), and weekly applications increased the likelihood of stress and injury to nestling and adult hawks. Between 2016 and 2020 we developed and tested a new treatment protocol. By applying a single dose of controlled-release permethrin (Permacap 1%) to the perimeter of the hawk nest, we successfully prevented parasitism by Philornis spp. This new treatment was as effective as the old one at preventing Philornis infestations, while reducing human labor, exposure of nestlings to insecticide, and disturbance at nests. As of 2020, this method has also been used to prevent Philornis infestation of nestling Puerto Rican Sharp-Shinned Hawk (Accipiter venator venator). Philornis with subcutaneous larvae, such as infect Ridgway’s Hawk and Puerto Rican Sharp-shinned Hawk, represent >80% of known Philornis spp. This new treatment may be suitable for preventing infestations of subcutaneous-feeding Philornis spp. in other susceptible birds of conservation concern.