I lost most of my older ducks over the winter only had 2 of the Blue Swedish left so I ordered 16 new Khaki Campbell ducklings all female. The older ducks are very happy to have new ducks around since they got big enough to introduce to the older birds.
I open the door so they can go out if they want to it depends on how much snow we have if it’s really deep they usually stay in or come out for a few minutes then go back inside. The ducks love the snow they will come out no matter how much there is.