It doesn't have to be a lack of space if you have an aggressive hen. As my signature says, I have 4 batches of birds. The lowest of the order when I got the 2017 chicks was Penelope a 2015 EE. To maintain her place in the order she chased all the 2017s when they got bigger. When they started going up on the roosts, she would chase them off then go back to where she wanted to spend the night even though I had 30' of roost at 4' high and another 8' at 2' high and a total of 18 birds. Of those 2 are parallel 12' roosts.
None of my birds has ever roosted on the 2' bar, they just use it to stage the 4's. Some of the young birds started roosting on the 1/2 plywood dividers for the 3' wide nest box. I put a slanted roof over the nests. Then they started finding places out in the barn alley to roost. I had to go out every night after dark and move them into the coop where they would be safe. I finally put a vertical divider in the middle of the parallel roosts so she couldn't easily cross to where the younger birds were trying to roost. Some of the younger birds were roosting on that! I took it out before it got too cold last winter since it isn't the sort of thing they can keep their feet warm.
