Chickens will lay in the winter - especially in their first season of laying - they just may not lay as many eggs due to the shorter days. Many people do put lights on their birds to encourage laying over the winter. In my personal opinion, it is better not to, as I believe in doing things as naturally as possible. Egg laying is a very intensive task and I think it is good for hens to have a chance to slow down and take a break. Allowing them a break means fewer health issues relating to laying (egg bound etc), and allows them to lay for longer. Because bottom line, the hen is born with all the eggs she will ever lay, so you won't get more eggs out of her by forcing laying on the shorter days - you'll just decrease the number of years she is a laying hen at all.