I live in MN and do most of my hunting in Iowa. We hit SD once a year as well.
I do well walking the road ditches. Figure out if the birds are using the north/south or the east/west ditches. It seems to vary each day depending on wind direction. Then start walking your dog. Having a corn field on both sides helps, but not a must. Late season I also start hiting the larger tracts of public land. Seems like the survivors will migrate back into the heavier cover when it starts to get nasty out. Plus most hunters are at home now and they don't get hit that hard anymore.