I live on Harstene Island near Shelton, 2 hours from Seattle. The best thing ever is a mix of fine bark mulch and peat moss. I've been doing this for 4 years now. The peat absorbs water and the mix doesn't turn into mud. The chickens love rolling around and dust bathing in peat. Even when they're digging around in the wet peat, it doesn't stick to their legs and feathers like mud does. Just don't ever use straw. It really starts to stink when it's decomposing in a wet environment.