Temporal Patterns, Behavioral Drivers, and Physiological Correlates of West Nile Virus Exposure in American Robins (<i>Turdus migratorius</i>)

AbstractComplex interactions between animal migration and infection are increasingly recognized as important for shaping when and where wildlife are infectious. Bird migration may facilitate spatial spread of zoonotic pathogens but remains poorly understood, owing in part to limited seasonal sampling. Using serology for immunoglobulin Y antibodies, we evaluated seasonal exposure to West Nile virus (WNV) of American robins (<i>Turdus migratorius</i>) sampled monthly during 2021 and 2022 in Indiana and compared our seroprevalence results to those of robins from previous studies across North America using meta-analysis. Because robins overwintering in Indiana include local breeders and those breeding farther north, we next evaluated how the probability of WNV exposure varied by breeding latitude. We also tagged robins breeding in Indiana with tracking devices to evaluate whether exposure to WNV is related to movement distance. We found that robins in Indiana are exposed to WNV more frequently than robins in previous studies elsewhere in North America and in earlier years, but we found no effects of season, sex, or breeding latitude. However, robins with higher fat scores were more likely to be seropositive, which may indicate that these birds are more likely to survive infection. Our tracking data indicated that robins breeding in Indiana migrate several hundred miles to overwinter in the southeastern United States and that WNV seropositivity had no association with movement distance. The mean durations of spring and fall migration were 13 and 19 d, respectively, nearly the same as or moderately above the maximum WNV infectious period in robins. Although these results suggest that American robins have the capacity to move WNV long distances in spring, further studies are needed across the range of this host species to uncover its role in dispersing WNV.