Thanks Duckchick2011!!
I will look into these suggestions. I hadn't considered ear infection before but the way he is acting definitely seems it could be inner ear related. His balance is way off. Thanks again!
We've lived in our house for 13 years and have formed a close relationship with a drake Muscovy who has lived in the lake behind our house since day 1. He has always been "top dog" in the duck community back there. :) About a week ago I watched him suddenly fall sideways and flop a little...