My bro's living in Spain and there they have a fair amount of stray cats as well. Which then got kittens, then.. then.. yeah. My bro decided to do something about it.
He managed to capture a few strays with their litters. And when they were old enough, he brought them to the vet. The strays who got spayed would get a cut in their ear. Left for male, right for female, or other way around, don't recall. It turns out to be pretty customary over there.
So if you'd see a stray with a specific cut in their ear you'd know they're already spayed and you don't need to take action. Maybe a good idea to introduce this idea over there?
@cajun_cheechako Considering the neighbor fail... probably not. 😅
@trinsec my brother mentioned that they also do that here, but not sure if it's universally practiced.