What Happened?

On yesterday's float, we were anchored up in a really good spot and the guys were working hard to nab a few fish.  While they were fishing, something strange was spotted floating down the river behind the boat.  The slow current eventually brought it right up to the boat.  How in the world did this large vulture end up dead in the river?  Any ideas? Stories? Original works of fiction involving a dead vulture on a fly fishing trip?