Dead Loons in the Great Lakes

Hundreds of dead loons have washed up on the shores of the Great Lakes in the last few months, and scientists say they don't know exactly what is killing them.

It is thought the loons died after eating bad fish contaminated with Type E botulism, a common bacteria which grows on the bottom of lakes and is spread by zebra mussels and quagga mussels. The mussels which are then consumed by fish, and the fish are then consumed by the loons.