The familiar Gadwall (Mareca strepera), a widespread dabbing duck, is a common spring and fall migrant in Wisconsin. Gadwalls are also occasional winter residents in the southeastern part of the state.
When you resemble one of the most common waterfowl species in North America, sometimes it's hard to stand out. Noting subtle differences and a careful eye, one can fairly easily pick a Gadwall out of a lineup of Mallards. If you see a group, make sure to be on the lookout.