I took moss from the backyard, dried it out and glued it to the underside of the roof and in little clusters on top. The roof underneath is painted a russet brown and then has been given a light coat of metallic bronze glaze. The rims around the openings as well as the little perch have been painted olive green.
I also took some bronze colored flat glitter (not shiny) and sprinkled a bit on top here and there admist the moss. The wood is actually tanbark from the front yard planting beds! I just made sure to pick out pieces of wood that were strips to have them more closely resemble "planks".