Sorry for the long post. I too have a somewhat wet run. Water from the hill behind it runs right through after a heavy rain. Personally I totally avoid pine shavings and pine needles in the run itself (I do use shavings inside the coop, though). If you're looking for something to break down in the run, the shavings take for-e-ver to break down (you'd probably have recognizable wood shavings even a year later), and pine needles are not absorbent at all, they'd just poke your chickens. My preference for my wet run is wheat straw and grass clippings. Lately I've been using mostly yard clippings since straw was in short supply, but I have close to an acre of pasture grass that I can mow and later go over with my lawn sweeper to pick up the clippings. I discharge the clippings, let them dry a day or two, then sweep them up. It keeps my 16'x16' run in good supply. I supplement with straw because it helps keep the girls entertained and aids in a good carbon to nitrogen ratio for composting. I just clip one of the two wires off the bale and let them scratch at it to pick it apart and spread it themselves to get at the seeds.
Even with good ventilation, after a few rains the floor does get pretty matted, and after we got 4" of rain in 10 days back in May, it was kinda smelly - but we literally had no sunshine and nonstop rain for 10 days. After a couple weeks of dry sunny weather and the girls scratching, it had mostly dried back out.
Regarding leaves, in a run that can get wet, I can't imagine leaves would help much as they mat worse, even when chopped up. For that reason I kept my leaves in a separate compost pile in the north 40 to make leaf mold.
Let me ask you this: what do you plan to use the compost for? Veggie garden mulch, soil amendment, flower bed mulch, all of the above? I initially planned to rake the littler from the run and finish it off by hot composting it and using it as a soil amendment in the veggie garden, but did ultimately decide that the straw takes too long to completely decompose for a soil amendment. What works best for me is instead using it as mulch in the veggie garden. Normally, weed/grass clippings and straw are full of seeds that would make your gardening life miserable in short order. After being in the run with my girls for a month or so, though, I'm confident we're 95%+ seed free. A few weeks ago, I raked out the straw/clipping mix from the run and used it as a thick, deep mulch around all of my veggies. In my mind it's perfect. Suppress weed growth, help retain soil moisture, and the added chicken poo helps feed my plants. In the few weeks since adding this to the garden I haven't picked a single weed from around the plants I used it on.
