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US Fish & Wildlife Service FieldNotes

A Deadly Brew: Avian Botulism and Microcystins

Region 5, December 21, 2012
Poplar Island Management Team prepares for collection
Poplar Island Management Team prepares for collection - Photo Credit: n/a
MD Dept. of Natural Resources veterinarian Dr. Cindy Driscoll rehydrating sick mallard
MD Dept. of Natural Resources veterinarian Dr. Cindy Driscoll rehydrating sick mallard - Photo Credit: n/a
Green-winged teal in microcystin layer
Green-winged teal in microcystin layer - Photo Credit: n/a

More than 750 birds and mammals were killed or sickened during a 15-week period from August to early November 2012 at the Paul S. Sarbanes Ecosystem Project at Poplar Island. Cause of death was attributed to both avian botulism and exposure to microcystins, a toxin produced by certain species of blue-green algae. Of special note is that the particular variant of the toxin, until now, had only been found in southern Brazil and western Canada. Thirty-five species were affected, with waterfowl and shorebirds the primary avian victims, and muskrats representing the sole mammal affected.


The response effort, led by the Poplar Island Wildlife Management team (Chesapeake Bay Field Office biologists Peter McGowan, Chris Guy, and Robbie Callahan), consisted of daily foot surveys to collect all dead and sick birds. Subsamples of freshly dead individuals were submitted for pathology to the USGS National Wildlife Health Center and the Southeastern Cooperative Wildlife Disease Study where avian botulism and microcystin exposure was confirmed.

Live birds encountered during daily surveys that appeared sick were collected and stabilized on site via rehydration, then transported to Tri-State Bird Rescue and Research Inc. for further treatment. Of the 213 sick birds that were collected, 188 were submitted for treatment, 70 survived and were subsequently released several weeks later.

Although the mortalities were unfortunate, the data pertaining to microcystin concentrations in bird and mammal tissues contributes greatly to the scientific literature regarding wildlife and microcystin exposure, which at this time is lacking. The response effort was greatly enhanced by volunteers from the Washington Office and the Chesapeake Bay Field Office. Special thanks to the Office of Migratory Birds in the Northeast Regional Office and Washington Office for technical and financial assistance during the response.

For more information contact:
Peter McGowan

Contact Info: Kathryn Reshetiloff, 410-573-4582, kathryn_reshetiloff@fws.gov