WAMBA said:
it seems like i barely ever see crows anymore and somebody told me it's because a lot of the population has been wiped out by the west nile virus--anybody know if that's true?
A very correct and apt observation! Yes; Crows - and the rest of the Family Corvidae including jays, ravens, and magpies - are among the most - if not THE most susceptible of avain species to fatal infection with West Nile virus. In fact, One of the first observations in '99 by Dr. Tracy McNamara, the veterinarian at the Bronx Zoo who submitted the first samples from which the virus was isolated and which proved that it had finally reached our shores, was that unusual numbers of sick and dead crows were being found in Bronx Park. Sadly, in December of '02 when I took a camping trip in the North Cave Hills of Harding County, SD the playful magpies that had always greeted me at my old campsite were nowhere to be seen. The next year the virus crossed the Rockies and is now found coast-to-coast. It's only this year that I hear they've finally begun to make a come-back.
One of the first birds positive for West Nile in SD was a bluejay we found in our woodlot in '02. Their population plummetted and, like the magpies, have only this tear begun to show evidence of a come-back. As is the case with most introduced foreign pathogens, initial catastrophic losses can be expected in the newly discovered (from the pathogen's perspective) supremely susceptible population. With time, a new balance comes to be established between the pathogen and its potential host populations, and life goes on.
In some situations, however, some of the new newly exposed host species may be rendered extinct before that mentioned "balance" is established with other local hosts. Such was the case with a number of native Hawaiian bird species after accidental introduction of the Avian pox virus and the Avian malaria blood parsite to the Hawaiian Islands.
Best t'ye,
Dave (y'r friendly neighborhood wildlife pathologist (ret.))