I've seen a feral cat stalking my young birds before in spring & would've shot it if my gun were handy. There are all kinds of cats around here - I'm aware that some are just mousers, but there are those that want something more filling.
I'm sure a cat or cats have killed some of my juveniles. I could not find any digs or places any critter could get in and kill. One morning I found 14 dead most just killed and a few with their heads off but laying next to the body. I saw a black cat lurking around so I suspect that it may have been the cat. A friend of mine who has a lot of chickens said he has had cats kill his and they just go in and kill for the killing and will kill several birds at a time. I put a live trap out for several nights but didn't catch anything. I do have electric wire around the bottom of my pens to discourage the diggers and it seems to work. I have heard critters make funny sounds like they had found the wire.