OMG there are at least 15 cats in my neighborhood. I have invited them all to dinner at my house, and am systematically trapping them, neutering, and releasing them. The reason there are at least 15 is because they are not neutered. Someone's gotta do it, so if it's that much of a nuisance to you, you do it, or there will be even more. Each female can have 10 kittens in a litter multiple times a year! I am trapping mine. Yes, they are released back, but I'll tell you what. I haven't seen a mouse in my house or on my property since they started coming around! I used to get mice in the house all the friggin' time. By the way, I have a covered large litter box outside for them. They use it! They use it, I change it, and we're all happy. The un-neutered males like to mark their territory, but if you fix them soon enough, that will stop. It's good of the cat lovers to feed these animals; theirs is a tough life, and only tough because of human negligence.
Not your fault, but it's not theirs, either. I'm so happy with our micelessness that I am building some houses for them to winter in. I sprinkle the yard with food grade DE to make sure we don't have fleas and ticks to deal with. I have found a way to co-habitate, so it can be done. I know I'm late with this, but had to add to it. I enjoy the cat watching as much as I do the bird watching...and yes, most of the birds manage to stay alive.