It was very strange, these two groups just ran to each other and snuggle together like long lost friends. I think maybe since there is just a few weeks difference in age? is why they have no problems being together? or perhaps being the same breed? I don't know but they get along great and have not had one incident of nipping. I will keep the youngsters in the pen for a couple more weeks or longer before turning them out. I know now they will follow the older ones. maybe the eleven of them will be a deterent to the three older mallards. ha.. like safety in numbers. I will wait till they are older as the mallards gave the older muscovies a hard time when I put the muscovies and mallards together. this is working out much better.