I spent the last winter rotating large mattress bags full of leaves around the yard here in Montana so my 5 hens could have bare ground to work on. So, I read this thread with great interest! The bags don't offer a place to roost and poop, but are lightweight, easy to move, and bring up lots of bugs and worms to the surface. Whenever I grab a bag the chickens are racing over to gobble up the wide variety of but protein that naturally rises to the surface after just a day or more. They end up pooping on the bug patch, as well as the rest of the yard, which seems to be enough to bring the bugs to the surface.
I don't see how to insert a photo, but will figure it out. I attached a photo as a file.
The mattress bags are free for the taking and tough enough to last over a year in the sun and weather. Initially they were to cover and insulate the root crops which I harvest in mid winter for the sweetest carrots and roots, but discovered how well they maintain little patches of green grass all winter. Whenever I move them I use the big scoop snow shovel to quickly clear a new spot right next to the current spot. The chickens jump right on the green patch and spend most of the day there if the ground is snow covered, like they're fenced in. It is also nice to have a large, year round source of dry carbon bagged up to use in the compost, and I use the leaves as bedding in the coop, too.
I have lots of friends with chickens confined to coops and runs instead of on grass and there is a noticeable difference in egg flavor, as evidenced by the trade offers that come in! I have been getting an egg a day per chicken since Feb 1, and their other food is compost and scraps of course, with a mainstay of local grown grains and legumes cracked with camelina meal and kelp especially for chickens for the same price as the imported feed.
I also installed this automatic chicken door in January so they would be safe at night once they put themselves to bed:
It works great and I opted for the solar panel and light sensor so the girls can be outside as soon as they wake up and stay out until dark. It's great to be away from the house at sunset and know that they are safe. I have no relation to the door company and it may seem expensive but it's worth it to me.