If they have a secure house out of drafts but still well ventilated then I'd keep them closed up that way you know they are secure and won't freeze. Ducks are very hardy and have a thick layer of down under their feathers so no need for heat at all. She may have been sick it is usually very hard to tell since they are prey and hide their illnesses well. sometimes until it's too late.Haha, yep none of those. At least not that we or anyone else have seen. We do have mice, though, and if the wounds on her legs happened after she died I wonder if mice were chewing on them once she passed. Which would still leave us wondering about the cause of death. The coop is warm, but we usually leave the little door open to the run unless it is extremely cold and blizzardy. We had no troubles with them during winter last year. I'm thinking now that might not be such a good idea if there's a possibility of a duck getting a "wild hair" thinking it will be okay to sleep outside.