For those of you who live in northern climates and keep chickens...What is it like caring for them in the cold months?  Do they need a heat lamp?  I've heard if you want eggs all year they need a light to keep the "days" longer.  We've always wanted to keep a few chickens for eggs for the family but I think the winter has put me off.  Can anyone offer any pointers or direct me to a good resource?

Thanks!