The Effects of Urbanization on Tick Parasitism Rates in Birds of Southeastern Virginia

The coastal region of southeastern Virginia is one of the largest urban areas along one of North America’s migratory flyways. Because hundreds of avian species use this flyway, understanding factors affecting birds and their health is of paramount concern. Within this region, 14 species of ticks have been documented, all of which may serve as vectors of mammal (including human) pathogens. By sampling birds at sites of varying levels of urbanization within the coastal southeastern urban matrix, I studied the relationship between ticks and their avian hosts, and how this relationship varies seasonally. Mistnets were set-up at five permanent sites and six ad-hoc sites between August 2012 and August 2014 to sample ticks from both migratory and resident birds. During this time, 1886 birds were sampled, and 943 ticks were collected from avian hosts. These ticks were later identified to species in order to determine species-specific avian hosts. Field sites were ranked qualitatively and then quantitatively using national land cover data and ArcGIS in order to determine how urban each site was relative to others; the proportion of birds with ticks was greater at less urbanized (more rural) sites. Percent impervious surface and season played an important role in predicting tick parasitism rates, as did bird life history traits, such as foraging and nesting behavior. The most common life stage and tick species collected from birds were larval rabbit ticks (Haemaphysalis leporispalustris), followed by larval bird ticks (Ixodes brunneus). This study demonstrates how levels of urbanization can influence tick parasitism rates on birds and increases knowledge of the corresponding relationship between urbanization and disease prevalence, which ultimately could affect human health risks