Strange wave makes every bird take off

When filming something else a little unrelated my camera caught a strange wave of energy (coming from the right upper side) that, when it hits the tree, makes every bird fly off at the same time. I didn't see this happen with my own eyes..but they obviously felt, heard, saw something that effected them to fly off like that.. I asked the building if they had some kind of pest deterrent and they said no and were just as surprised as I was. What is it? Where did it come from? And does it effect us too?