I have 11 ducks all together, 9 teens and 2 adults, the adults go outside for most part during the day and will occassionally sleep outside at night to, but I'm way to soft hearted and they have me wrapped around their little webbed feet, I see them shivering, or holding their legs up and in, well the male can but with my female she can't because she was born with a birth defect that holds the other leg up as if she is doing it on her own but not. So she has to lay down to keep warm. The male has had a ice chunk on one of his toes. And then they stand at the slider looking in, pecking at the window as if they want in and so I let them in. It's just the 2 of them so I feel I should bring them in at night because between the two I wonder if they can truly keep each other warm. Then I have the 9 teens in that hatched in October that can't be outside yet full time, but when March/April come around I will start putting them outside depending on temps, I am right now only for a short time to get them use to it and possibly their bodies adapting to it. I'm debating on putting them all in the garage while I'm on vacation they'll be out of the wind/rain/snow, ect but still may be exposed to frigid temps if it gets to terribly cold. But most likely they'll remain in the basement because I'll even worry that much more of their well being. But next winter, they will be outside since there will be more of them for body heat to keep each other warm and I'll have a nice shelter built. But I will bring them in during dangerous temps or heavy snow/freezing rain.