To the question of chickens roosting in trees and their safety.
When we were growing up we had chickens and plenty of them. My dad loved the old fashioned mixed breed barnyard banty. We had probably had 40-50 on the place at any one time.
They would roost in the trees spring, summer, fall and winter. They seemed to prefer the ash and wild cherry trees.
Anyway, they survived just fine. Occasionally you would here a comotion at night but not very often.
These chickens were the closest thing I think to "wild" chicken as you could get. They were extremely fast and excellant flyers. They could go to a branch 30 feet high in a blink and take off and fly, soar, fly, soar. When I saw them fly across the yard or across the cow pasture they always reminded me of a ringneck pheasant when they flew.
The hens would hide their nests and bring back a dozen or so chicks. The chicks seemed to be the ones who suffered from predation the most, generally a hen would only raise 2 or 3 to the time they could start roosting in the cedar trees.
When we became "overran" with banties dad would simply get out his 22 and we had chicken soup.
I do remember one time as well dad bought some white leghorn battery hens from some place and within 6 months those things started roosting in the trees, however, they didn't last long, it may have been the white color that attracted predators.
Anyway, I don't recommend letting the chickens roost in trees too many things can go wrong with this arrangements.