Scientists are stepping up efforts to learn where and how many Great Lakes water birds are getting fatal food poisoning.
The U.S. Geological Survey says around 100,000 may have died since 2000 from Type E botulism. Their bodies have littered beaches. Loons and other deep-diving birds appear especially vulnerable.
Researchers in Florida are using stuffed bird carcasses in a lab tank to develop a model that could trace their movements and pinpoint where they were poisoned.
It's part of a broader effort to determine what, if anything, can be done to stop the die-offs.
Experts believe the toxin is produced when algae dies, floats to the bottom and rots, sucking up oxygen from the water.
The toxin moves up the food chain until birds eat contaminated fish and become paralyzed.
Explore further: Great lakes waterfowl die-offs: Finding the source