Place the pheasants into a large slow cooker. Wrap and drape the bacon over the birds, covering the pheasants as much as you can. Whisk the condensed soup, sour cream, water, chopped onion, onion soup mix, and mushrooms together in a mixing bowl. Season to taste with salt and pepper. Pour over the pheasants.
Cook on Low for 8 to 10 hours, or on High for 5 to 7 hours.