Light is the most likely issue, but also breed choice. Some birds are just better at laying over the winter than others, while some (ahem, polish) stop laying at the first leaf fall (at least our girls do). I remember someplace, maybe Gail Damerow's book on flock keeping, there is a column for chickens that have a tendency to lay over winter. You could also google it and add a few of those girls to your flock at some point. Our super blue has not stopped laying, she is still going strong, an egg a day even when everyone else stopped. We are also in AZ so have a lot more light than you up in NY, so that may not mean much.