Well, in my country (Cyprus) there are so many stray cats that they are becoming a nuisance to say the least. I mean, I used to have cats when I was younger, and before I moved to the UK I had to get a couple of cats to handle a mice and snake infestation in my garden, and the funny thing is that whenever I put some food out for them, all the stray cats would come to eat, so my two cats eventually became part of that same pack and left me, and I had to feed them all to keep them to come in my garden to take care of the mice and snakes. I remember once I counted 18 cats just lying on the lawn (I did eventually take measures to keep them from coming, it was just too much).
I don't want to stir the conversation any more here, but I have to say, from my experience, cats will hunt birds as they always have. The real monster is not the cat, it's the man. I mean, in Cyprus, illegal hunting is responsible for the death of 5.000.000 birds every year, and it's done with nets and sticks covered in glue. I mean, whenever I saw a cat killing a bird, I would say that that's nature working. But a few years ago, when I was hiking I found a 20meter rope covered in glue, with a couple of dozen birds stuck on it. If I had the guy that put that thing there in front of me at the time, gawd I was so angry, I would make him regret the day he was born. It took me a little less than two hours to get all the birds off the rope, clean them very carefully from any glue residue (most of them still had some on their feathers but I don't think that it would affect their flight), released them, and cut the rope down. I had to do this on my own because I had no phone reception there (needless to say I called the authorities as soon as I was back to civilisation). Those are the real monsters, not cats. And the worst of all, only 3 of the birds that were on the rope had any market value, the rest would just be left on that rope to die, or killed and left there. THAT'S waste.
To be honest, I don't really like cats. They are not really good pets, they will double-cross you on the first occasion, not loyal like dogs for example, and they have a weird personality as pets. But they are animals, and part of nature, and they follow their instincts. Yeah, owners should do their best to keep them from being a nuisance to other people, but if they do get around, they will kill other small animals, that's in their nature.