I have been wondering this myself. I hear different things all the time. I have round dowels in my chicken coop because that is what the plan called for. And I have tree branches in the run. They seem fine on both (I was wondering if a dowel is not ideal for the chickens?). In my turkey house I did have a 2x2 for a roost when they were a little smaller I just recently put a very large tree branch in the coop for roosting. And an even larger one in the run. They seen to do fine on both also.
For my question:
I am building a new coop. And it will house standards and bantams (Marans and Japanese bantams) So what should I do for a roost for them? I was thinking a 2x4 but doing it the skinny side up. Is that ok? does anyone with standards and bantams do anything special?
Dowels are harder for them to grip because being ground-dwelling birds, their feet are more used to being flat, compared to flying, tree-dwelling birds, whose feet are designed to grip a round branch.
A 2x4 with the wide side for them to sit on is the best. This allows for their feet to be flat, so that they can fully cover them in the winter and keep them warm.