Urbanization and tick parasitism in birds of coastal southeastern Virginia

Abstract

One of North America's major avian migratory pathways occurs along a large anthropogenically modified coastal region of southeastern Virginia, USA. Because hundreds of avian species migrate along the east coast of North America, understanding factors affecting birds and their health is of ecological and conservation interest. Within southeastern Virginia, 14 tick species have been documented, all of which may serve as vectors of vertebrate pathogens. We tested 5 hypotheses to understand how varying levels of urbanization within an urban matrix of a coastal region affected avian parasitism rates. We sampled resident and migratory birds for ticks across an urbanization gradient at 5 permanent and 6 ad hoc sites from August 2012 to August 2014 and determined parasitism rates at the landscape and site scales. At the landscape scale, the proportion of birds parasitized by ticks was reduced at more urbanized sites. Urbanized sites were largely associated with higher water and impervious surfaces in the surrounding area, which may have prevented dispersal of ticks or hosts to isolated urban locations, and lower tree cover, which likely reduced tick survival because of decreased leaf litter. At the site scale, properties associated with being on or near the ground (i.e., foraging guild and age) were the best predictors of tick parasitism. These findings demonstrate that the effects of urbanization are neither uniform nor straightforward. In addition to affecting avian species composition, anthropogenic changes to the landscape are affecting the relationship between avian hosts and their parasites, a finding that has important implications for avian conservation efforts and management practices.

Tick infestation of birds across a gradient of urbanization intensity in the United States Great Plains

“…Unlike prevalence of tick infestation, intensity of infestation was unrelated to urbanization. Previous studies show a link between large-scale land use and ticks, hosts, and pathogens (Allan et al 2003;LoGiudice et al 2003;Heller et al 2019). Our results suggest that even if the proportion of birds carrying at least one tick is influenced by urbanization, numbers of ticks carried by infested birds can be more consistent across an urban-to-rural gradient.…”

“…A study in the eastern U.S. found that birds in areas with extensive impervious surface (i.e. more urbanized areas) and water bodies were less likely to carry ticks, but percent imperviousness alone did not predict infestation (Heller et al 2019). Pathogen prevalence in ticks carried by birds may also vary in relation to urbanization, as indicated by a study showing urban birds are less likely to carry B. burgdorferi-infected ticks (Hamer et al 2012b).…”