Ironraven, I was backing you . I too wear dark colors in winter, for the same reasons.
eeph, maybe standing still, not much. But, and I'm sure you seen it, looking at someone who has recently exercised, through a thermal lens, you can clearly see the excess heat rising off the body. Moreso in the head area, if thats its only vent out (due to clothing).
So, I think that convection WILL play a part in this, given the above situation. The human body will do what it can to release excess energy in the form of heat. HEat is transferred to the blood vessels closest to the surface of the skin. As there are far more of these on the head, than any other body part, due to the fact that the brain is selfish & will attempt to regulate its temp the best it can, it only stands to reason that we lose more heat through the head than other parts. Also, the head has little fat on it (for most of us ), and thus requires thermoregulation through convection.
Wow, ok, my brain now hurts. Alot.