I love the idea of a spirea. I have a hot corner of the run that would really benefit from some intensive shade. I think I'll see if I can get my DH to find one on an old homestead and dig it up and transplant it. If I can protect it for a little while with a tomato cage, it would be a great addition to the run.
Danz, you might want to check & see what kind of bushes will grow in your soil, I had clay soil when I lived outside of Derby & it was the pits. I worked on areas there for 23 years until I moved breaking down that junk. You have to add a lot of organic matter to the soil to break down that clay. I don't know if it would make it there, but my chickens love this huge spirea bush I have over by the driveway beside the garage. It has grown just huge & it drapes all the way down to the ground so they can all get under it if they're scared or in the heat. It blooms white flowers in the spring. I usually spray it with water in the heat of the day so that it drops water droplets down on the chickens to cool them & I also spray some under the bush so they have cool ground to lay on in there. It's their favorite place to hang out when it's hot.