Not related to aviation, but once I had a problem with bird droppings
associated with a yagi type antenna
on a ship. I solved it by installing a windmill (made from anemometer
parts) above the antenna. Worked like a charm - so that is definitely a
valid approach.

Once I saw a plane with one of those plastic owls mounted on one of the
prop tips (which was positioned vertically). Don't know how well it
worked, since it wasn't at my home airport, and I never saw the plane
again.

David Johnson