in my 2011 post.
Both mergansers occur during migration in Minnesota. Red-breasted Mergansers winter along the coast of North America, while Common Mergansers do not venture into the southeastern states. On the other hand, Red-breasted Mergansers breed further north than do Commons. One consequence of these differences is that relatively little is known about Red-breasted Merganser biology (Craik et al. 2015).