Any ideas on what caused the die-off over 8,000 birds along the shores of Lake Michigan in 2007?

Invasive populations of zebra mussels and round gobies -- which arrived in ballast tanks in the 1980s and 1990s -- spreading over the Great Lakes and effectively creating a new food chain.

Zebra mussels and their deep-water kin, quagga mussels, filter naturally occurring botulism and other toxins from the water. Gobies eat the mussels, and birds, in turn, eat the gobies.

Scientists theorize this new food chain is concentrating botulism and other toxins and passing them up to predators. The theory is the subject of a handful of scientific papers and upcoming research proposals but in effect its a typical bio accumulation or magnification issue. The toxin is only toxic to the high order consumers who eat the gobies which individually have moderate levels of the toxin but the birds eat hundreds of gobies therefore the toxin builds up to dangerous levels. Its also possible that many other organisms are effected at moderate levels and may even be killing inconspicuous animals withing the food web.

I think that the overall health of the ecosystem including pressure on the birds for food and space would have increased the effect of the toxin because of stress. It shows the impact invasive species have on ecosystems and how easy it is for us to alter and permanently damage natural ecosystems through seemingly innocent actions such as dumping ballast. Will We Ever Learn.

nope. i have no clue. it had to be anatural disaster, or something of the sort. in a hury. bye.