Might be your best bet unless you can find more females. but then you still don't have any guarantee the drakes still won't fight, I had 2 drakes to 10 girls till this past summer when i decided to keep another drake from a hatch ,and those boys still would fight and get bloody. No telling what is going to happen this spring, actually i already have one of my drakes my oldest separated from the other 2 because he is old and not doing well and of course they pick up on stuff like that. If your calls and mallards pair then it may be best to just keep to 2 pairs and find a home for the one drake.Right now the calls are in the coop and the mallards are in the pen because the mallards wouldn't go up into the coop. They are again separated for the night. Would it be better if I sold one male mallard, so I would have a pair of calls and a pair of mallards?