You can technically road/ditch hunt in SD. You can't do it from an improved road like a highway. You also can't shoot from the road surface.

It can get a little tricky. You can walk into the ditch and basically you can only shoot the bird if it is flying straight down the ditch. You can't shoot across the road and you also can't shoot if the bird is over the fenceof private property. If it falls on private property you can go get it but can't take your gun.

Most natives DON'T like it and you are best not to plan on doing it. Like was said if you need a bird and see one on the way home you can try to kill one but there is a lot left to interpretation if someone gets upset.