An obvious question but it needs to be asked....do you have bird feeders in your yard? When I rented I had four or five feeders in our urban environment. We moved to a more suburban location three years ago and I put the feeders out in the spring. By the start of summer I decided to take them down because the birds were using the pool rails as resting and pooping spots. Took a couple of weeks but they no longer congregate so close and taking down the feeders solved the problem.