Brettski, I would feel honored if we had hooded mergansers nest at our place! Wood ducks are easy to get. Yes, they will eat a few little fish but not enough to make a difference.
For about 3-4 days, we had more snow geese around here than I've ever seen in my life. Northern SD and ND got a heavy snow which drove them back south to our area. Literally tens of thousands of them everywhere you looked. There would be a flock of 5-10,000 in a field and a couple of miles down the road, another flock of the same size and on and on. A few were shot but not many. It's warm today and they're gone!
