These ducks are known for their elaborate courting displays; this is part of the "Head-throw-kick", described by Birds of North America thus: "male thrusts his head straight forward, then lowers it to his rump with his bill pointed back past vertical, at which point he utters a single, grating call, thrusting his head rapidly forward (sometimes flicking it from one side to the other) while kicking water out with his feet." For the final stage, the kick, see http://www.pbase.com/image/148701260 .