Interesting comment about the sunny side vs. shadow side. I observed the exact opposite thing during the cold snap as well. When I scouted, all the birds seemed to like to huddle on the cold side of the river which I noted as odd but whcked them in the shadows the following day (and froze my butt off in the process).
I'm wondering if there is a pattern to be followed or if its just the fact that they go to the side that they like and don't really care.
I do not know, I have normally hunted the shady side of any river to hide more than anything else, however, for hose few days when the cold really set-in I noticed all the ducks and geese suning. I also saw ducks on the shady side where they normally go, however, 10 to 1 they went to the sunny side.
I hunted Sunday afternoon and I also saw alot more ducks on the sunny side than in the shade. I think that if all things the same and the sun is out the birds enjoy the sun just like us.