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West Nile virus
self portrait - circa 1996

 

Dear Friends:

There has been a lot of questions and concern this past summer about the arrival of the West Nile virus (WNV) in Michigan, seeing dead or sick birds and what we can do about it as bird watchers. From everything I have read (I am not expert on the subject) eliminating mosquitoes with sprays is not the only approach to the situation and there are safer options such as treating water with organic and non-toxic compounds eliminating mosquitoes before they have a chance to multiply.

Many experts suggest draining ponds and birdbaths. With drought-like conditions this past summer I think this action may have stressed the birds even more and perhaps made them more susceptible to disease and infection. Most ponds are recirculating and mosquitoes will not lay eggs on moving water, and if birdbaths are changed daily mosquito eggs do not have a chance to develop. There are also organic products to place in or spray on the water’s surface to eliminate a mosquito’s ability to lay eggs on stagnant water.

To put the threat into perspective we found several interesting notes from Julie Craves, bird expert and bander at University of Michigan-Dearborn. Ms. Craves says:

-- WNV has been present in the Old World for decades. Bird populations have not suffered.
-- The crow population alone represents millions of birds. Single roosts of crows can contain 200,000 birds.
-- Outdoor cats kill TENS, probably HUNDREDS, of MILLIONS of birds ANNUALLY in the U.S.
-- Window strikes kill between 97 and 975 MILLION birds (that is not a typo) annually in the U.S.
-- Communications towers kill between 1.2 and 5 million birds annually in the U.S.
-- As for the human perspective, the flu kills about 20,000 people a year.

The following are copies of web posts from Julie Craves found at North Michigan Birding:

Subject: Dead birds and West Nile Virus
From: "Julie Craves"
Date: 16 Aug 2002 7:22am

Once West Nile Virus (WNV) has been confirmed in a county, the state health department usually no longer accepts birds for testing -- they are overwhelmed. WNV has been confirmed in Wayne, Washtenaw, Oakland, Monroe, and Lenawee Cos. in southeast Michigan.

Birds can and do die of many causes. I think a good percentage of the reports I'm hearing these days are due to [heightened] public awareness of dead birds because of the WNV hysteria. Unfortunately, I have had reports of suspected mass poisonings of crows due to unfounded fears. Here are the facts: -- In an area where the virus occurs, only 1% of the mosquitoes will be infected. -- Of those bitten by one of these mosquitoes, only 1% will become seriously ill. Nearly every (all so far?) person who has died has been elderly or had some pre-existing immune disorder. -- Most people infected with WNV never have any symptoms. A few will have mild flu-like symptoms that last a few days.

Be sensible about prevention. Spraying campaigns do far more harm than good, both to humans and non-target organisms, and mosquitoes develop resistance to the pesticides. Spraying programs are initiated in response to public demand that agencies are "doing something." For a good article about this, see the National Audubon web site.

(Post #2 from Julie)
Subject: Re: WNV is a threat to many bird species
From: "Julie Craves"
Date: 16 Aug 2002 10:13pm

WNV has been common and widespread in the Old World for decades. Birds eventually build up immunity to it. Like humans, most birds that become infected show no symptoms. Outbreaks tend to by triggered by the right combination of environmental conditions, susceptible birds (i.e., juveniles), and thresholds of infected mosquitoes and birds. They flare up and pass.

Rest assured this is one of those hot topics that will spawn funding for all sorts of research, keeping graduate students busy for the next several years. I do recall a couple of big environmental groups endorsing bird-related research; since being discovered in the 1930s, plenty has already been done on the human front.

Julie A. Craves
Rouge River Bird Observatory
University of Michigan-Dearborn
www.umd.umich.edu/dept/rouge_river/

Interesting uh? For more information on product options to control mosquitoes please ask one of our Naturalists the next time you visit J.J. Cardinal’s.
      Louise Dawson
(update to hyperlink 02/04/03)

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originally posted 9/24/02 illustrations, text & fun © J.J. Cardinal's 2002
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