Between 200 and 300 common loons were found dead along the shores of Lake Ontario in New York, the state Environmental Conservation Department said. Besides the loons, long-tailed ducks, grebes and gulls were found, state conservation office said in a release. The birds had type E botulism. The department said a mortality event involving so many loons has not been seen on Lake Ontario since 2006. First documented in waterbirds from Lake Michigan in the 1960s, type E botulism was recorded off and on for about 30 years in the lower Great Lakes, state environmentalists said. Since the late 1990s, however, type E botulism in birds has become an annual event in one or more of the Great Lakes, resulting in very large kills in some years Two non-native species, the bottom-dwelling round gobies and quagga mussels, state scientists said in the release posted Friday on the department's website. The botulism toxin generated in near mussel beds is picked up by the mussels, the preferred food of the round goby. So far this year, all known botulism mortality in diving birds in New York has been confined to the eastern basin of Lake Ontario. Bird carcasses did not wash ashore until late October, the majority in the last two weeks.