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Unexplained Waterfowl Deaths Recur in Colorado

January 7, 2008.

From the Colorado Division of Wildlife:

The Colorado Division of Wildlife (DOW) has learned that duck mortalities are occurring again this winter in some Denver metro-area wastewater treatment facilities. 

On December 24, the first two northern shovelers were found at one wastewater treatment facility.  Since then, 30 more dead ducks have been reported by two other facilities.  All of the metro-area wastewater treatment plants are reporting an influx of ducks into their facilities over the last two to three weeks that has coincided with an extended period of freezing temperatures along the northern Front Range.

Recent weather conditions are similar to those that occurred about this same time last year when approximately 1,000 ducks died over a several-week period.   Most of the ducks found dead last year were northern shovelers.  This species spends most of it’s time in the water and inhabits waters of wastewater treatment plants when natural wetlands freeze over.

During the investigation of last year’s duck die-off, multiple state and federal agencies worked together to attempt to determine the cause.  All of the common duck infectious diseases were ruled out, including avian influenza, botulism and avian cholera.  The general consensus from wildlife experts was that the cause of death appeared to be related to loss of waterproofing of feathers.  Investigations to date have failed to identify a single causative factor for the loss of waterproofing.

The U.S. Fish and Wildlife Service, in cooperation with the DOW, the U.S. Geological Survey, and the metro wastewater treatment plants, will be continuing to investigate the cause of death for local northern shovelers.  Metro Wastewater Reclamation District, which has experienced a small fraction of the duck deaths this winter, is providing a working location to perform an experimental study that will augment information gathered from field investigations.  Ducks will be exposed to the various wastewater sources in a controlled manner to determine which factors may be leading to duck deaths.  The study will continue through the end of February.  Investigators hope the information gathered will help lead to improved practices for reducing losses of wild waterfowl that use these plants during the winter.

As was done last year, the wastewater treatment facilities will be looking for sick and dead ducks on a daily basis.  Any sick ducks found at the facilities will be brought to a licensed rehabilitator by DOW volunteers.  The public is encouraged to report any sick or dead birds by calling the Colorado Help Line at 1-877-462-2911.

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