We had/have the same issue but thankfully they are moving. While having 30 ducks around all the time was annoying it was the pigeons that were the real issue. We had bird shit everywhere!!! We had problems keeping our pool chemicals in line and there was so much bird shit on our roof that our gutters were clogged up and growing weeds. I had asked them multiple times to please stop feeding the birds but even though they said they would stop it never ended. I was nearing the point of calling the police about the issue because it is a violation of city code but I never wanted to be that neighbor.

I would suggest talking to them and if that doesn't work then you may have to get the police involved.