Inland WI... No picnic. You got the Great Mississippi to the West, and you got Lake Michigan to the East. Where are the birds? To the East and West of the state. Plus we are right inbetween the Canadian prairie and the Eastern shore, so our general migration is fairly small compared to the areas around us. Gettin a limit is not an easy thing to do inside the state. The amount of water in WI is huge. Well over 10,000 classisifed lakes in the state (that doesn't include smaller ponds or marsh and swamp land), and most is surrounded by timber so the nesting habitat for mallards and geese is limited, but amazing for woodducks. This keeps ducks pretty spread out. Makes it extremely hard to find a HUNTABLE concentration of ducks, year round, inside the state. Field hunting is also difficult, because most farms are 200 acres or smaller and other then the southern part of the state, most private parsals are 40 acres or less now. So many old farm homesteads have been divided and pieced off for more land profit. We just don't have the large fields that the dakotas, iowa, kansas, and southern illinois have.
Not to mention the hunters. No one knows how to call, but they think they do. Most are a bunch of DUMB rednecks that just come out to shoot their guns at whatever. And most only hunt opening weekend, not caring enough about the sport or its resources. On opening weekend I would guess at least 2/3 to 3/4 of the local ducks are taken. Then you won't see most hunting ducks until next year. If I were to estimate, 75% of duck hunting licenses sold in the state, are never used again after opening weekend. The few that do care about the resource, don't educate themselves on the art of waterfowl hunting, calling, and decoying. So they just become educators and the few birds that are left become really wise to hunters.
The way I've found to be successful is to hunt late when there is ice to take out alot of the lakes and rivers for ducks to seek refuge. You have to find the huntable spots at this time, but if you know what you are looking for, you will find a concentration. Also scouting and good calling is key.