West Nile Virus Impacts Birds
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Posted by Rosemary Drisdelle Jun 22, 2007 |
Authors of a paper published in the May 17 issue of Nature report that seven species of North American birds suffered significant population declines since West Nile Virus appeared in 1999. The paper, titled “West Nile Virus Emergence and Large-Scale Declines of North American Bird Populations,” details a study that used 26 years of data from the Breeding Bird Survey to follow the populations of twenty bird species. The focus of the research was to determine whether bird populations declined after 1999 and whether any observed decline could be attributed to bird mortality due to West Nile Virus.
Some of the twenty bird species studied were predicted to suffer a moderate to high impact from West Nile Virus infection, while others were predicted to be minimally affected, based on the known mortality of the disease in these species (some species of birds suffer serious illness while others seem to tolerate the infection well). Predictions were correct for six of the seven impacted species: American Crow (the most seriously affected with a 45% decline), Blue Jay, Tufted Titmouse, American Robin, House Wren, and Chickadee. For the seventh species, the Eastern Bluebird, no prediction had been made because the seriousness of West Nile Virus infection in this species was unknown.
Most of the bird populations have not recovered—only the House Wren and Blue Jay have regained their former populations from lows in 2003 and 2004 respectively. It seems that West Nile Virus is doing even more damage to birds than it is to humans, and it’s part of the reason so many North American birds are in decline.
Read the article:
LaDeau, S. L., A. M. Kilpatrick and P. P. Marra. “West Nile Virus Emergence and Large-Scale Declines of North American Bird Populations,” Nature doi:10.1038/nature05829
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