I built a large chicken coop, with a large fire pit for warmth.

What happens is once you have a bunch of chickens, they wander the border of the pen & end up "piling up" in the corners. For some reason, I end up with two of the four corners piled solid with chickens. They eventually form a type of pyramid, and were climbing up & out over two levels of 2x1 stone at each corner. I ended up needing to put a roof over it.

Their wandering AI could use some dev tuning.