I would like to use wood chips from chipper. Have been unsuccessful at getting them so far. Someone else with dump spot close to road always beats me out when line crews are working in area. If you can get them, they are free as the crew likes to find a convenient place to dump them. You will get 10 15 yds at a time too.
So I use grass clippings from our yard. We mow around 5 acres so we never run out. I will use leaves, wild honeysuckle and straw in wintertime. I keep litter 6" deep in coop. I like grass since it smells good and is free. Chooks dive in and eat some of it when it first gets dumped in coop. They still have grass in their run tho, but thinning out now that winter almost here.
If I could get the free chips I used to get, would use those and then recycle to garden. No way I am putting grass clippings in garden for mulch tho. Enough work as it is to keep it weed free without seeding more in! Still, am grateful to have free mulch, even if it is not my first choice. May build and use poop planks for wintertime. Easier to keep odor down that way as fresh litter more scarce in wintertime. Can always dump poop onto garden all winter and let rain and time do it's work.