Neighbors nuisance cats is a very common problem.

You need to let your neighbor know what is happening and that its not acceptable. You give them a chance to fix it first.

If that doesn't work then you trap the cat (have a heart trap and a can of tuna) and turn it over to animal control, as a captured stray.

If this poor cat - yes, poor neglected animal, acting out on hormones due to the fact that his owners did not care enough to neuter him - so, anyway, if this cat can be neutered, I bet a lot of this behavior will go away.
Blame the human, not the cat :[

We have a similar problem -- a neighbor's cat comes and starts "fights" with our cat through the patio door. I have no idea whose cat it is, although it is wearing a collar.

We've tried two things:

1) We put up a motion detecting animal sprayer. This worked quite well, but was a pain in the butt to keep going constantly, because a) we have no grass to push the stake into (our backyard is all concrete patio) so we had to come up this complex fort of bricks to hold it up, and b) turning it on and off so the gardener/pool man/etc didn't get soaked got annoying.

2) We got some super stinky anti-cat spray from the garden store and sprayed it on the patio. This seems to have worked well at keeping the cat away. Downside: when I say it's stinky, it's stinky. When my husband was spraying it, he was taken by surprise at how strong it was, and started backing away coughing and trying to keep from getting it in his eyes...and fell into the pool. Yes, I laughed my ass off at him.

I'd start by talking to the neighbors. If that gets you nowhere (which is likely), I'd try one of the above solutions. Personally, I think trapping the cat and taking it to animal control, while tempting, is rather heartless. It's likely a virtual death sentence for the animal, and if there are other solutions to try first, I'd go with those.

The cat is not a stray if the owner is known and there is no leash law for cats in your jurisdiction. If you can't resolve this issue with your neighbor, then call animal control and discuss it with them. They will inform you of your legal options, and if trapping is one of them, then animal control should handle that for you.

There are also cat deterrents on the market. You might check into them and see if there is something you can spray or apply around the perimeter of your porch to keep the outside cats away. I believe there is also a sprinkler available that is activated with a motion sensor. If the outside cat gets sprinkled every time (s)he approaches your porch, it probably won't take more than one or two encounters to convince the cat to stay away.

You could also keep your own cats inside the house and out of the porch at night so that these close encounters can't happen.

Laurie

Thanks for all of the ideas....I will have to look into the water sprayer. That should keep the squirrels from getting too close too.

Do not trap the cat and have it brought to the shelter. Let animal control talk to the owner.

Too many people send pet cats to their deaths and that's nonsense. It's a human problem, not a cat problem.