From Bob Russell, U.S. Fish and Wildlife Service:

The open water at the south end of Lake Pepin held an estimated 17,000 Common Mergansers Tuesday afternoon, a wonderful site in the afternoon sun.  My estimates might be a bit low because last week's aerial survey tallied over 20,000 in this same area but some of the missing birds may have been down river towards Reed's Landing.  Several dozen eagles were readily apparent, some grabbing fish from mergansers that had overestimated what they could swallow quickly. As far as I know this is the world's largest concentration of this merganser, a magnificent and annual spectacle that is overshadowed by the eagle concentrations that occur at the same time. 

The message originally was published on the email network of the Minnesota Ornithologists' Union.