When I see some recommending a wide flat surface for them to roost on to keep their toes warm I usually smile and go on. They are birds that roost and as such they like to grip the perch while they sleep. If you go out and look at them roosting most of them will be on the front edge of the perch with their toes hanging over the edge no matter how wide the board is. If you are going out there also note that they are sitting down fluffed out and the toes are covered with their feathers, to the point that you can barely see their toes if at all. Add to the fact if they don't move, the perch it self gets warmed by the chicken, think of a warm bed. In my book once you go over say two inches all your are doing is adding more surface in the coop to clean. Frost bitten toes usually happen when they are up and manage to get their feet wet on a really cold day, not when thy have them tucked in and dry at night.
