Following on from the otter thread one of the most common predators around my way is the pinemartin. I see one most weeks, have bolted them from log piles, seen them nesting in peoples lofts on several occasions, got them in the hen house a few times, they show no fear of humans and stand their ground when cornered, everyone I know with chickens has had big losses due to them, and there was one eating cake the other day the wife had put on the bird table.