Hope I can help, we raise mallard ducks and had to keep the ducklings in the basement in the spring because of the cold weather...I agree stinky! Messy and alot of work. We built a couple portable pens that we finally moved them into that would take a heat lamp while it was cold. The only other alternative would build a pen with fencing or netting over the top and add extra length of fencing around the bottom of the pen ( about 1 foot ) and bury it into the ground laying it out at an angle away from the pen ( about 6 inches deep). If something tries to dig under the fence it will hit the buried fencing and will not be able to get into it. Right now we have a flight pen with 350 mallards in it , extra fencing around the bottom and netting over the top and haven't had anything get into the pen. Although we have a nightly visitor...owl that sits on the posts and wishes he could break in. We didn't do this with our chickens and lost 3 last week so live and learn,,we now have netting over the top of them too.