The west nest box was empty when I checked a few minutes ago and I was able to get a count. The duck actually left without covering the eggs. When I checked the camera playback to see why, she was sleeping and then she opened her eyes wide and sat for about 1 second, then jumped for the door and left. Something startled her but I could detect nothing unusual. It was quiet (there was a good sound recording) and nothing visible that seemed abnormal.
There are 20 eggs. 19 of them are wood duck eggs but one is a hooded merganser egg: it is slightly larger, rounder, and whiter than the wood duck eggs. For the photo below I put it in the center, on top of the others.
She’ll come back fairly soon. It’s not unusual for a duck to leave suddenly when startled and they typically don’t stay away for very long. Also ducks don’t have much sense of smell and are not disturbed by my counting and slight rearranging as long as I put things back the way I found them … except in this case I covered the eggs with the down blanket when I was done counting and taking a picture, more or less as she would have done if she had left normally.