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3929Fwd: Corvids & West Nile

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  • Stephen Long
    Apr 1, 2005
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      >This year, we birders on the left coast should begin to see some
      >drastic reductions in Corvids due to West Nile Virus. A "Short
      >Communication" in the February, 2005 Condor, entitled: "West Nile
      >Virus Devastates an American Crow Population" (by Carolee Caffrey,
      >et al.), documents what happened to a well-studied, color-marked
      >population of crows in Stillwater, OK when WNV showed up. The
      >pathogen causes very nearly 100% mortality in infected individuals,
      >echoing the experience of American Native Peoples encountering a
      >"new" pathogen for which they had virtually no immunity (smallpox).
      >West Nile arrived in the geographic area of the study population in
      >June 2003. By the end of the year, 65% of the study population had
      >died (2 out of every 3 birds), and the mortality amongst fledglings
      >was a whopping 82%. This compares to pre-WNV mortality levels of 2%
      >of adults & 34% for fledglings.
      >Although the authors were careful to point out that their study was
      >confined to a single corvid species, it is not unreasonable to
      >predict similiar devastation to at least congeners of the American
      >Crow, if not the entire Family of Corvidae in North America. Which
      >brings us to California, where birders have for several years been
      >reporting an increase in Corvus populations -- that trend is now
      >likely to show a sudden and precipitous reversal.
      >Frankly, I'm not too worried that crows and ravens are going to
      >disappear from the California avifauna. But I do admit to some
      >concern over the low-population endemic Corvid of California, the
      >Island Scrub-Jay. Other birders and ornithologists will have much
      >more information than I about the threat to this taxon, e.g. is
      >there sufficient breeding habitat for mosquitoes? I'd be interested
      >in hearing from others.
      >While there is virtually no data on what constitutes the WNV
      >"season" in California, it would not be unreasonable to assume that
      >it mirrors the season elsewhere in North America, namely
      >June-October. So by this year's Christmas Bird Counts, we should
      >begin to have an idea if the California corvid populations are
      >Knowing my own birding disposition with regard to crows & ravens --
      >see the first one of a day, then ignore all the rest -- I've had to
      >discipline myself to begin to count them. Birding just became a
      >richer activity!
      >Stephen M. Long
      >Museum of Vertebrate Zoology
      >University of California
      >Berkeley, CA 94720
      >Telephone: 510-642-8299
      >Telefax: 510-643-8238
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