This fall is turning out to be the deadliest yet for loons, ducks and other birds that encounter a natural outbreak of a rare form of the nerve toxin botulism in Lake Erie.
Ward Stone, director of the New York Department of Environmental Conservation Pathology Laboratory in Delmar, N.Y., which studies the dead birds, said that over the last two weeks his staff had picked up more than 5,500 birds along the shores of Lake Erie in western New York, between Buffalo and Dunkirk, including 126 loons, 4,500 long-tailed ducks, geese, grebes, mergansers, scaups and many types of gulls. He said the birds found were only a small part of the total number killed. "We're very concerned," he said. "This is the tip of the iceberg."
Canadian wildlife officials have also found large numbers of birds on Lake Erie. They have counted more than 1,000 dead loons, including 700 on an 18-mile stretch of beach at Long Point, Ontario. Loons are of special concern because their numbers in the region are low.
The birds died after eating fish infected with type E botulism, officials said.
The botulism outbreak killed thousands of resident birds in the same area this summer. Those that have died in recent weeks are migratory waterfowl moving south. It is the fourth year the bacteria have appeared to kill birds, and no one knows how many years it might last.
This year, New York wildlife officials, who are gathering as many carcasses as they can find, are trying a new approach, hoping to head off the poisoning of eagles, hawks and other scavengers. The toxin does not pose a threat to humans, officials say, as long as they do not eat fish or ducks that appear to be healthy.
This is believed to be the largest outbreak of type E botulism in the United States, and it is believed to be caused by an invasion of exotic species. A proliferation of quagga and zebra mussels, brought from Europe in ocean-going freighters, has greatly cleaned the water in Lake Erie, allowing sunlight to penetrate to much greater depths and increasing the production of weeds. Botulism thrives in decaying weeds and is apparently ingested by the mussels, and another exotic species, a fish called the round goby. Birds die when they eat the gobies or mussels.
The outbreak is expected to end when the lake cools sometime in the next couple of weeks.