Changes in climate, land use, and biological communities can affect disease and parasite infection rates and virulence. In the northern Great Basin, fire and invasive species have led to the conversion of shrub-steppe ecosystems into non-native grasslands. The conversion to grasslands has negatively impacted black-tailed jackrabbits (Lepus californicus), the preferred prey of golden eagles (Aquila chrysaetos). In the absence of jackrabbits, golden eagles select other available prey and, increasingly, rock pigeons (Columba livia) are becoming a larger part of eagle diets in southwest Idaho. Rock pigeons, and other columbids, are vectors for Trichomonas gallinae, a protozoan that causes the disease avian trichomonosis. T. gallinae infection can cause the development of oral caseous plaques large enough to inhibit feeding, eventually leading to starvation or suffocation of nestling raptors.
A warming climate may also allow ectoparasites to expand their natural ranges. Cliff-nesting birds are susceptible to ectoparasite infestations, especially hematophagous ectoparasites. In 1996, McFadzen and Marzluff reported a northern range expansion for Mexican chicken bugs (Haematosiphon inodora), an avian ectoparasite in the Family Cimicidae (commonly known as bed bugs). Raptor nestlings in nests with heavy infestations of Mexican chicken bugs may exhibit decreased development, physiological condition and stress. The effects of heavy ectoparasite infestation can cause premature fledging and nestling mortality. In addition, changes in land cover may reduce the ability of golden eagles to actively “defend” their nests with aromatic shrub species that may deter insects from parasitizing nestlings.
Both trichomonosis and heavy ectoparasite loads have been observed in golden eagle nests in the Morley Nelson Birds of Prey National Conservation Area, with negative impacts on nestling survival. Unfortunately, studies of T. gallinae and ectoparasites in relation to golden eagle nesting ecology have been infrequent and potential impacts on golden eagle populations are unknown. My project examined the prevalence and infection risk factors for trichomonosis and hematophagous ectoparasites affecting young golden eagles in southwestern Idaho. I am investigating the relationship between nestling diet and T. gallinae infection, studying the ectoparasite community, examining the effects of ectoparasites on nestling physiological condition and survival, and determining if aromatic green plant material in the nest may alleviate the negative effects of nest ectoparasites.
This project includes collaboration with biologists across western North America to better understand the range and extent of disease and ectoparasites in golden eagle populations. This information collected from this study will be used to better understand how the effects of T. gallinae and ectoparasites may impact the productivity of North American golden eagle populations.
To learn more about Ben’s research, visit his project website at: https://benjamindudek.wordpress.com/