Odd Common Merganser feeding frenzy (Maine)

For many years I was aware that hundreds of ducks congregated in the center of a large local lake here in Maine.

I assumed (quite wrongly) that they were buffleheads and/or blue bills (scaup), but never took the time to really check them out.

I used a large hobby astronomical telescope to observe them last weekend (too far away and too fast moving for a spotting scope)

It turns out they are common mergansers - brazillions of them. They surrounded and entrapped masses of small (unidentified) fish and busily gobbled them up. When the bait moved - so did the birds. It was a real frenzy. They churned up the water, splashing it everywhere. A large number of gulls (mostly ringed bills) and a bald eagle joined in too.

I've observed pelagic seabirds doing this, but not mergansers. This appears to be an annual ritual for them on their way down the local river system on their fall migration.

Would make for some fine natural history documentary footage...

(and the pine grosbeaks are back too)