Feral Cats?

While I was busy cleaning the fence I managed to find the carcasses of two more dead birds.  They were in the same general area as the one I found a couple of days ago, so many they were all killed at about the same time?  They were both sparrows too, which makes me think that they were all whacked at once.  Just like the original one, it looks like something got at them because their heads were pretty well beat up and their necks looked twisted almost all the way around.  Maybe someone has a cat that they are letting roam the neighborhood.  I did see a cat in the backyard last fall that apparently belongs to someone a couple of blocks away.  At the time it was crouching watching the birds at our feeders, so maybe it finally figured out the best place to sit and stalk them.  Now I will have to keep an eye out, because I really don’t like the idea of a stray, or some other cat roaming around in my yard!