During my visit to Churchill Manitoba, we observed many species of waterfowl flying. The main species were common eider of the Hudson Bay subspecies.
We also identified two of the three species of merganser that are present in North America. The only item that they all have in common is a serrated bill. The serrated bill also gives him the nickname of “Saw-Bill.”
The common and red-breasted species can be confused when making an identification. A couple of points that help with identification are that the red-merganser is that both sexes have red eyes while the common merganser has dark eyes. Also, in-flight the red-breasted merganser upper wing with white secondaries and coverts have two dark dividing bars while the common merganser has only one dark dividing bar.
The breeding grounds for both species can overlap but the red-breasted merganser has a much more northerly range extending up into the arctic circle, and they nest on the ground while the common mergansers are cavity nesters.