I agree. I mix ducks all the time. As long as there is sufficient space per duck, there won't be carnage most of the time. I've had the odd plucker now and then, but I think it was a nutrition issue. Once totally on pasture, they are fine. (of course, once they are 2 months old, problem ducks become freezer birds.)I usually wait until the younger one can get around a little bit before introducing it to bigger babies. I've got a batch right now that has an age difference of ten days from oldest to youngest. No carnage, just waited until the new babies could stand and move around okay.