West Nile virus and large-scale declines of North American bird populations

Emerging infectious diseases present a formidable challenge to the conservation of native species in the 21^st Century.  However, identifying the impacts of an introduced disease and distinguishing it from other forces that influence population dynamics requires abundance data that extend before and after pathogen introduction.  This work draws on avian population dynamics over two decades to evaluate recent impacts of West Nile virus (WNV) on twenty potential avian hosts across North America. The hierarchical Bayesian analyses identified statistically significant declines in population abundances for seven species that agree with a priori predictions from limited laboratory experiments and the spatio-temporal intensity of pathogen transmission.  American crow populations declined significantly after WNV emergence across North America and up to 45% regionally, with local extirpation at individual routes likely.   Six other peridomestic species, including American robin and blue jay, also demonstrated statistically significant declines following WNV emergence, ranging from 10% to 48% reductions in some regions.