For the past few years, Several boats moored in Staten Island's Great Kills harbor, including mine, have been progressively bombarded with Seagull poop and food remains. IMHO, this has been an unfortunate side effect of cleaner local waters attracting more bait fish. I have tried everything from nets, fake owls, snakes, and cats, to motion detecting solar lights with only limited success. This year, I finally got a break. One of our yacht club members quit his membership and abandoned his boat at the mooring, about 100 yards from mine. As the season progressed, his boat became more and more covered with fish blood and guts which nobody cleaned away, unlike the boats of active members. As a result, his boat became the hangout, restaurant, and latrine for the local gulls, sparing nearby boats the mess. They are attracted to the smell and find safety in numbers. Check this out