Chickens love kale. Does kale survive a typical winter where you live? There might be some other frost-hardy plants that can be left in the field until the
chickens scratch the snow off of them, although I admit this probably means one grazing even per winter per plot.
It might also be possible to have large windrows of coarse woody material with a little "green"
compost material: I'm thinking you might not want
enough nitrogen to make it thermophyllic, just enough to keep it warm. That way, instead of paddocks of plant matter, you can rotate through paddocks of detritovores. When the chickens have scratched up most of the worms, millipedes, woodlice, etc., move them on to a new windrow and re-build the one they have turned & manured. It might be necessary to somehow cover the tops & sides of the windrow (chicken wire?), so that the chickens work from the ends not the top, and the detritovores can stay warm until the chickens get to them. Depending on your conditions, it may even be possible to grow the compost material in the location that you later build the windrows.
The long edges of a warm, composting windrow might offer
shelter for some plants grown for the chickens, allowing those plants to survive farther into the winter.
"the qualities of these bacteria, like the heat of the sun, electricity, or the qualities of metals, are part of the storehouse of knowledge of all men. They are manifestations of the laws of nature, free to all men and reserved exclusively to none." SCOTUS, Funk Bros. Seed Co. v. Kale Inoculant Co.