We'll here in CO there's not a whole lot of marshes and thick timber to hunt ducks. We hunt ponds before they freeze then the rivers/fields during colder part of winter for waterfowl. Try going to the colorado DOW website and clicking on the "state wildlife area's" you should be able to find a spot near you. As for big game we hunt mule deer and the seasons just ended. There are some whitetails way out east but we leave them for the local boys. Head to the high country for elk and mule deer hunting, lots of great opratunitys for big game hunting on public land in CO. The DOW website has all the info you need, that and a little scouting and you'll be set. anywhere along the colorado and platte rivers will be good.
BTW most of the public waterfowl hunting spots on the east are by reservation so you might want to check into that.