Dratted Bird Update

Haha. My bird technique won, I no longer have to worry about nests being built in my sailcover. But there is a trickledown effect, I look 2 boats to starboard at the marina and I see the ugliest contraption rigged up of a line parallel to the boom with about 10 CDs tied to it to scare the birds away. Doesn't work, Bob saw a bird fly out of his sail cover. Oddly enough, I've never seen a person on that boat and it has never left the marina as far as I can tell. How'd the person know that he had a bird infestation?