I'm noticing more of the chickens taking to the roosts lately, so will just see if they all eventually 'get' the idea. This is a young flock (5 months). My nest box is a larger 2-seater which may contribute to the night time nest box snuggling. I also have a vent/window behind the roost which I sometimes forget to close at night and that likely has a brisk breeze to it (faces the prevailing wind). I'll get better at that.