Finding the Source of the Great Lakes Waterfowl Die Off: Where Water Birds Perish

In the Great Lakes region, birds are dying off in large numbers. Loons, gulls and other waterfowl are falling to deadly Type E botulism, a neuromuscular disease that's caused when birds eat fish infected with toxin-producing bacteria. Now, scientists have taken a closer look at this disease in an attempt to find its source. That way, they can help prevent future die-offs in the area.

Cases of Type E botulism are on the rise. In 2007, about 10,000 more waterfowl died than when the disease was first reported in 1963. Better understanding its origins is crucial when it comes to future prevention.

The researchers used their expertise in experimental hydrodynamics in order to develop a method to track waterfowl carcasses. This, in turn, could help determine the source of lethal outbreaks that infect fish eaten by waterbirds. In order to create this technique, the scientists performed towing tank experiments on submerging bird carcasses to determine the relevant drag coefficients. With wind and current data, these coefficients could be used in probabilistic source tracking simulations to calculate waterbird drift velocity and direction in order to reconstruct the likely routes that bird bodies may have traveled after a die-off.

"Using the submerged front area of an ellipse, together with the frontal area of any submerged portions of the bird's head and neck gives good similarity across the range of speeds and submergence levels tested," said Karl von Ellenrieder, one of the researchers, in a news release. "This is the first effort we are aware of to obtain estimates of force parameters operating on drifting waterbirds for incorporation into a current and wave-based tracking model."

The findings are crucial for not only monitoring the spread of disease, though. It could also be useful for tracking oil spills. Learning exactly where water birds originate from could allow scientists to better prevent disasters in the future. As water bird deaths continue to increase, this is particularly important.

The findings were presented at the 66^th Annual Division of Fluid Dynamics Meeting in Pittsburgh.