I've been trying to introduce two ducks into my flock for about a month. They are about two months old. I've had them in a wire crate where the chickens and other ducks can see them, but not reach them. I've been letting them out in longer increments at first with supervision, and then alone, but every time I do so the chickens, specifically two that I know are lower in the pecking order, will attack and pull feathers even if the new ducks are paying little attention to them. It's gotten so bad that they've injured one of them, so I put them back up in the wire crate to heal, but when they came back out, the chickens went after them again. I've never had this problem when introducing ducks before, and I don't want them to get seriously injured or killed. It seems by now the chickens would get the message that the ducks are not trying to outrank them. What should I do? I don't want them to be locked up all the time.