I've planted Nanking cherry shrubs inside my run, with a poultry wire hoop around them the first few years until they're well established. They are pretty, very hardy here in this windy, dry, sometimes very hot and sometimes very cold climate, and provide small edible cherries that birds (including chickens) really like and will make a windbreak and a nice little shady area for the hens to collect under in a few years. . The other deciduous shrub that might work in the west is serviceberry, pretty, quick to grow, some edible fruit, very drought tolerant. Both of these sucker something awful, but the chickens would help to control that with their scratching and picking at anything green that tried to come up outside the boundaries.. I also bought a sad little pear tree at a clearance sale from Home Depot last year (for $5) and planted it in the middle of the chicken yard for shade - wire fence around it initially, and some rocks around the roots to keep them from being exposed, and it's doing great. My hens free range most days, but it's nice to have a little "landscaping" - and some cover - in their big run when they can't.