I find it curious that most of the reports of staging mergansers
have mentioned that more males are involved than females. I had understood
that all (??) ducks and geese paired off in the winter quarters and migrated
up together, as a pair, to the female's breeding area. Unfortunately, I
don't have the appropriate literature to check on timing of pair formation
of Common Mergs here. If these birds are staging, and they pair off in the
winter then why are there so many unpaired males? I wonder if these are not
staging males, but rather groups of un-sexy, unpaired males. If this is the
case, one would predict that the groups should include a good percentage of
young males and that they will linger on until late in the season. This type
of situation I have noticed in Buffleheads, however those flocks were almost
strictly of young males.

Alvaro Jaramillo "You are better off not knowing
Half Moon Bay, CA how sausages and laws are made"
alvaro at quake.net Otto von Bismarck,
but I saw it in a fortune cookie!

http://www.quake.net/~alvaro/index.html