I heard on the morning news awhile back, after the bird ordeal, that scientists think something spooked the birds. It was nighttime and they don't see in the dark very well. They believe that they collided with whatever was in their pathes at take off. Birds are easily injured and consequently died from it. I don't know but I don't believe that it was anything else.
As far as the fish, I've seen this happen back home in MD. I honestly think it's nature's way of keeping populations under control.