I have a lot of cats around the farm - some are half feral. One in particular would stalk the half grown chicks, even managing somehow to get them out of the pens. But - he never bothered with either the hens, or the small full grown bantams. Our neighbour had a lot of problems with hens going missing, and the culprit there was actually a badger, who she caught on cctv. Another neighbour had hens taken by birds of prey, and they plucked the hens in the field.