Clarks Hill Lake in Georgia was home to seven bald eagle nesting territories a few years ago. Today, only one nesting territory on Clarks Hill remains. The culprit is Avian Vacuolar Myelinopathy, or AVM, a mysterious syndrome that has killed thousands of coots and dozens of bald eagles in the southeastern United States, says a Georgia Department of Natural Resources newsletter.

While the exact cause of the syndrome is unknown, it is connected to the cyanobacteria Stigonematales. Stigonematales likes to grow on hydrilla, an invasive aquatic plant. It appears as though the coots eat the hydrilla, which has Stigonematales growing on it. And the bald eagles eat the coots.

Bald eagle and coot deaths tend to peak around November of each year.

Read more about this mysterious syndrome and more non-game news in Georgia Wild, the newsletter of Georgia DNR’s non-game and natural habitats program.

Photo: Hydrilla draped over a man’s hand. Courtesy of the US Fish and Wildlife Service.