Yesterday and today there was no sign of the Long-tailed Duck at Peace Valley, but I did get a chance to watch a pair of Common Mergansers in their copulation display. The female was prone on the water with her neck outstretched and her chin touching the water. She faced the male as he circled, dipping his bill in the water then raising it up pointed to the sky in a ceremonial drinking display, mixed with occasional brief preening of the back feathers. This went on for more than ten minutes as I watched yesterday before I had to leave. Never did see if they actually did the deed. I couldn't find any photos of this behavior online, though it is described briefly in the Birds of North America account online (subscription required). I sure need to get that camera!