Buy a 50 pound bag of CLAY kitty litter, not the fancy one with smell reducing crystals or the clumping kind: just plain old cheap kitty litter. Dump it liberally on the poo and it will suck the moisture out of the turds making them easier to pick up when dry. You do NOT want to do this when rain is expected for a few days to a week. If this area is too large to use kitty litter, then the best thing for you to do is get as much up as you can, and then use a high powered spray nozzle on your hose to spray the offending doody out into the grass. As long as it is mostly gone, the water/feces mix will fertilize your grass, but use a lot of water. Next year, remove the dung after it freezes, don't be lazy like the dogs who don't want to walk to the trees. Leaving it all winter only makes a spring problem for you as you see.