Right there with you. We have a pretty serious feral cat problem in our area as well, and it's exacerbated by neighbors that have half a dozen or so of their own they allow to wander everywhere, and none of them have collars. I have talked to them, and their response has been "Well, there's not much you can do to control a cat from wandering, is there? haha". We also just recently discovered that one of the ferals dropped a load of kittens on the other side of one of our fences....so whee, more ferals. *sigh*
The cats have chased off most of the squirrels, killed a large number of birds, and generally terrorize the other animals in the area. I enjoy hearing birds singing and watching squirrels and rabbits go bounding about the yard....
I've taken to popping every cat I can with a BB gun every time I see them, but that only scares them off for awhile. Tried the mothballs on the perimeter (in glass jars and 'free-range' around the fence-line) and that also worked for a day or two. I have contacted Animal Control, but apparently I am not the only one with a feral cat problem....all of their cages are in use and booked for a spell. I don't have the inclination to purchase a live trap myself, as it would cost money I'd rather put towards our chickens; and to be honest, I don't have the time or money to "fix and release" or re-home them. Our local Shelter is over-crowded as it is, and the last thing they need are a few more cats to add to the mix. I've put calls in to the Animal Control center regarding eliminating the feral cats on my own, but have yet to hear back from them. Discharging a firearm in the city limits (and I am in the city limits) is, so far as I can determine, illegal. I don't want to use poison, because I'd probably end up doing more damage to the wildlife than the cats....and the BB gun isn't powerful enough to kill, only wound. I don't want to injure the cats, as that would be cruel....I just want them gone or dead. I know they are aware that there are chickens in the run, and I don't want them to get any ideas. I know that cats will probably not mess with a full-grown chicken, but my girls have a-ways to go before they reach that point. I am also fairly certain that the coop and run are secure, but I've read too many horror stories on this forum to have complete faith in that fact.
So....after a long-winded ramble (and thank you, OP, for allowing me a place to voice my concerns), I completely understand why you did what you did.