We had ducks on the docks and nesting in bushes. I persuaded a few neighbors and the local daycare that the yard was suitable for dog walking and play on weekdays. No ducks.
Cormorants on the main cover. Now I tie it with a peak and they can't perch. No cormorants.
Big birds would perch on the spreaders. I strung a fishing line ~ 6 inches higher. No big birds.
Now grackles perch on the roller furler and topping lift. With no bigger birds to scare them off, there are more birds and poop than ever. I could string something flashy, but if they are barely scared of me, what would that matter, other than one more thing to do before heading out?
I may try relocating the topping lift (boom in gallows and pull forward).
I'm at the end of the row in the marina and they simply like the spot. Other boats are clean. I've learned to like poop.