"Bedding" is mis-named when it comes to chickens. It's really 'litter', like in a horse's stall or a cat's box. It isn't for them to sleep in or on, but to absorb their waste. Basically, any animal that drops its waste continually needs something to soak it up. Without some kind of carbon-based bedding (anything natural that seems dry and dusty is probably carbonous: wood shavings, straw, leaves, etc.), their poop makes an enormous mess, smells awful, and is very unsanitary. With a nice, thick layer of bedding, the chickens' droppings fall on it and get absorbed/ mixed in, making it much cleaner and less smelly. (Some people use sand, which is more like cat litter: the droppings don't really mix in, but it's easier to rake them out and dispose of them elsewhere.) Litter + chicken droppings = a great manure/ compost for the garden; every time you clean out the coop you can dump that stuff into the compost heap or onto an unused garden bed. Save $$$ on fertilizer!
I use leaves in my chicken's run, but not in their coop. Leaves are great fun to scratch in, but aren't terribly absorbent, so I wouldn't want them under the roost. I use pine shavings inside.
As earlybird mentioned, you'll get much better responses by posting in the forum!
