Thank you all. I have tried to get these before without success. I was very lucky this time. I saw them downstream on Lake McDonald creek and thought I would wait upstream as they were making their way slowly up. I set up with my 300 + 1.4 and monopod and waited only about 5 minutes and they swam right past me. Beautiful duck.
I just wish I could improve on the presentation somehow. I never have used a flash, thinking it would make them scatter. That would give a catchlight. Anyone have suggestions?