Are mandarin ducks cold hardy

[luludaxia]

I have 4 mandarin ducks and I'm in Ontario, Canada. Now they are kept in a pen in our barn, which is not heated, and now the lowest temperature here is minus 6 to 8. I wonder if the mandarin ducks are cold hardy enough to spend the winter in a unheated barn or they must have heat?

 

[Kevin565]

Will the barn be free of any drafts?
The biggest concern for them would be frostbite on their feet. This should be avoidable with open water and plenty of dry bedding.