Here are a few more tips for cold weather, in addition to what "Dakotazeb" has outlined:
I wear long underwear bottoms - makes a difference when it's windy. And chaps!
Also, there's snow on the ground. A pair of high gaiters are great for keeping the snow away from your legs or underwear. I wear them under my pants as the brush/weed keep pulling them down.
A heavy sweater works well and is easily removed in the field, if it gets too warm.
For the hands: buy some handwarmers to slip into your gloves; they can make a big difference. I wear a heavy glove on my left hand, different glove on the right. Still experimenting with gloves...when it's very cold, and difficult to find the trigger, the birds have the advantage!