My guess is that it's a screened in area so that humans can get in there and the chickens can play outside without varmints getting to them. Just as I started this entry, he sent me this picture which I LOVE!
It's a diversion from the ballgame. 1st inning and the Mariners are already losing. Sigh.
EDIT: I get it!!! He just added the chicken ramp. So cool.