Quacking Around

Several ducks are hanging around the pond behind my house. One pair of mallards is nesting on the small strip of land, an isthmus of sorts, jutting into the water. Although this pair is clearly mated, tonight a couple of free-flying males landed on the water next to the nest. One of them popped up on his hindquarters, flapping his wings and quacking as he did a little dance. Was he trying to entice the female? I didn't see her stepping off the nest.
A couple of weeks ago I spotted a strange black and white duck diving in the pond. At first I thought it was a hooded merganser, but than I grabbed the binoculars and saw the duck lacked the distinctive crest of the merganser. This duck was pretty similar to the mallards nesting near the pond, but just lacking all color. Even the bird's beak was grey. The duck totally looked like a goth, completely dressed in black with a white face. Thanks to Ducks Unlimited, I discovered this duck is a bufflehead. Although Minnesota is out of this species' range, I not only spotted the bufflehead on the pond a few times, I also saw a bufflehead pair floating on the Missisippi river in Hastings. Has anyone else out there spotted a bufflehead? Let me know in the comments area.