A rare bird has been flying over the Great Lakes recently, and it isn't migrating or searching for prey. This hawkeyed species is a Learjet aircraft outfitted with an advanced imaging system. Engineers modified the plane to monitor algae in western Lake Erie and Lake Huron's Saginaw Bay. Most algae are harmless and even important to the health of the ecosystem. But when algae grow rapidly enough to form blooms that float on the water or wash ashore, they can be a nuisance.