I think they are more concerned about staying with the group than staying warm. If such a bird is not part of a flock in good feather then ranging habits will be more consistent with staying warm.
My birds generally do not drop feathers like like those you have shown although one that layed particularly hard late into season does look similar and is now afforded more protection.. It does cause temperature stress when it is cold. The supplements, if consumed in excess relative to the...
Protect them from wind. Baldness is usually indicative of more than just most. Up protein in diet to well in excess needed for egg production. Show current picture of birds.