September 11th, 2021, 10:14 a.m. local time

The mallard and their brethren receive attention on my blog from time to time.  Usually, it’s due to geese flying into my Moon shots.  Today, I went for a walk on a very pleasant day, taking a path I usually don’t travel.  As I was ending my journey, turning at a trail bend, I saw this sight, of a row of ducks, all sitting on the stonework overlooking the water.  I approach as stealthily as I could, and not daring to get any closer, took pictures of the fowl gathering.

I count 20 brownish-ducks on the stonework, and one white-headed, green-necked duck in the water (you can just see the white head in this picture, right next to the seventh brown mallard from the left).  Is the number 21 significant here?

If I understand correctly, the brown ducks are the females and the large, white-headed duck with the unfortunately-not-shown beautiful green neck, is the male.  Assuming this correct, what exactly is happening here?  The females appeared to be resting and barely stirred as I cautiously walked by.  The male swam back and forth, as if patrolling the line.