Hooded Merganser question

[Jodi Nielson]

I stumbled upon a group of about 20 Hooded Mergansers this morning in an out of the way little pond.  What struck me as odd was that there were females and non-breeding males but no males in breeding plumage.  Why is that?

[Charlie Spencer]

6 hours ago, Jodi Nielson said:

I stumbled upon a group of about 20 Hooded Mergansers this morning in an out of the way little pond.  What struck me as odd was that there were females and non-breeding males but no males in breeding plumage.  Why is that?

In many species, the breeding males migrate before females and immature / non-breeding males.  They do this to establish territories, and a few start nests, so they're ready when the females arrive. 

I saw a couple of flocks of mergansers like this a few weeks ago.  I don't know for certain this migration practice applies to mergansers but I'm guessing that's the case.  I've also seen flocks off all-female Red-winged Blackbirds.

[Jodi Nielson]

Thank you @Charlie Spencer.  I hadn't thought of the males doing recon while the rest bring up the rear, but that makes sense.

[aveschapinas]

15 hours ago, Jodi Nielson said:

I stumbled upon a group of about 20 Hooded Mergansers this morning in an out of the way little pond.  What struck me as odd was that there were females and non-breeding males but no males in breeding plumage.  Why is that?

I know nothing about the habits of Mergansers, but I have noticed that the Great-Tailed Grackles here hang out in single-sex groups except during active mating. So in a group traveling together they will tend to be all males or all females/immatures (they can be hard to tell apart). Then you see them in mixed groups during active courtship and raising young.