I've never been a bird owner, but I know that pet birdies are supposed to sit on natural branch perches instead of straight bars because the natural irregularities in the branch are better for their feet- a strait, uniform bar forces them to keep their feet in the same pose, while natural branches allow them to adjust a bit. Would it not be the same for chickens? ...well, I guess I dont know how a chicken rests. Do they perch on their feet, or settle and rest their weight on their tummies? Do their feet relax, or grip the roost? I imagine them gripping the roost, but now I am wondering.