Let me put my birdwatcher and wind sailing caps on here: Cormorants were highly susceptible to eggshell thinning from DDT and like other predatory birds in North America were nearly extinct by the time it was banned. They sure came roaring back though; at about the point where Lake Ontario flows into the St Lawrence River on the Kingston side of the islands there was this very picturesque little isle, Snake Island, that had several mature hardwood trees creating beauty natural beauty all over the place, summer and winter, that was until the cormorants started nesting in the trees in the mid 1980s and their acidic guano killed every green plant on it and laid the place bare down to the limestone in just a few years.