West Nile virus devastates an American crow population

In its spread west across North America in 2002, West Nile virus (WNV) reached a population of marked American Crows (Corvus brachyrhynchos) in Stillwater, Oklahoma, in late summer. Within two months, 46 of 120 individuals were missing or known to be dead, 39 of which (33% of the population) are estimated to have died for WNV-related reasons. In 2003, 56 of 78 marked crows disappeared or were found dead between June and November. Five of the 28 juvenile losses were possibly unrelated to WNV, thus we estimate that 65% of our population died because of this pathogen in 2003. The total loss of 72% of population members, including 82% of juveniles, in a single year of WNV exposure raises concern for precipitous declines in American Crow populations in coming years.