My ducks and chickens were in the same run until a couple of weeks ago - it stank, was always muddy even though I had put in some hardcore with sharp sand on top. Then when the snow was deep and crisp etc etc I felt sorry for them so when I emptied their shed one time I left the straw on the snow. Since then I have just kept doing that and also put the ducks in a separate run. Much cleaner and easier to walk on tramped down straw, they have clean water and the ducks can do what they like with theirs.