Will my quail be alright in subzero temperatures?

I have 6 Mountain Quail and 24 Bobwhites that are in adjacent pens with an attached shed for them to go into when it's too cold and so far they've all done fine throughout the harsh Maine winter here -- however, the forecast for tonight and tomorrow is around -25°F (with the windchill going as low as negative 35 degrees) and I'm wondering if they'll be alright in those kinds of temperatures. I did close them inside the shed for the night and the doors and windows are closed but it's still below zero in there and will likely stay that way for at least the next 48 hours or so. I'm more concerned about the Mountain Quail since there's fewer of them and they don't huddle together like the Bobwhites do, and while they've endured bitter cold temperatures before it still hasn't been close to 20-35 below zero so far this winter. I tried putting a heat lamp in the shed but there was a strong persistent burning smell so I took it out. Will they be alright at those temperatures or should I try and do more to keep them warm?