There have been incidents of birds dying from botulism, in 2000 and in 2002. Birds affected included grebes, common and red-breasted mergansers, loons, diving ducks, ring-billed gulls and herring gulls. One account suggests that bird populations are in trouble, notably the wood warbler, which had population declines around 60% in 2008. Possible causes for declines in bird populations are farming practices, loss of habitats, soil depletion and erosion, and toxic chemicals. In 2006, there were concerns of possible bird flu after two wild swans on the lake were found diseased, but it was learned that they did not contain the H5N1 virus. There were sightings of a magnificent frigatebird, a tropical bird with a two-metre wingspan, over the lake in 2008.