Since corn will not make your bird warmer if you want to
"supplement" with something in the winter add a little extra protein.
Chickens eat to fill there caloric intake and by feeding corn they will eat less feed because the fill caloric need sooner.
Also poultry tend to be "hotter" when fed or over fed a high protein feed and that is why your big egg producer will drop the amount of protein they are feeding in the hottest summer months. (by dropping the amount of protein intake they lessen the chances of Heat Stress in there birds)
Chris