About a hundred Mallards have spent the winter on the little stream that links the two large lakes in the Vadnais Reservoir system. It seems like there are many more males than females swimming around, with a few low intensity conflicts developing as they show off to one another (and the females).
The floating mobs of males exhibited several behaviors I have never seen (or paid attention to) before.
The latter behavior seem like a low intensity version of the more assertive wing-flap males perform while raising themselves slightly out of the water. Occasionally, the bob with arched neck ended in a chase of another male. The first 30 seconds of the video below illustrates better what I am trying to describe. (Click on the link to start the video in Viimeo.)
Mallard Courtship & Rivalry #1 from Steve McDonald on Vimeo.
These behaviors seem to be for the purpose of establishing male dominance, rather than to attract a particular female, since there were very few females around the male mobs.