When I was living in Missouri I we shot every cat we saw. Funny there were always more, probably 10 for everyone that was shot. I believe 100% that cats are increasingly destructive to several species of birds and rabbits, virtually any small game. Cats are almost perfect hunters and most survive where other animals might not. Cats kept as mousers are just as likely to breed like crazy and start killing everything but mice.
What constitues cruel and where does conservation of other species come in? Poison is unnecessarily cruel but so is shooting if you suck at it. Why is it any more humane to have the pound kill them as to put a bullet in their heads? Have your chickens or rabbits killed when you've been paying to feed them for a while and it's a little easier to do.