What is this behavior about?

[NYRIR]

I have a year old mallard drake in with 2 mallard females and 3 cayuga females...all for about a year.This year I added 7 pekins (both sexes) and have had no problems.I then added 2 mallard drakes from this year.One,who is really a quiet duck,is being chased down by the oldest mallard drake,mounted,and mated? Or it sure looks like it!The second younger mallard drake is not bothered by him at all.I also added some even younger (anconas and runners) They are not bothered either. Any ideas? Is it simply the personalities? Why does it appear he's mating?? I KNOW it's a young drake.If it's dominance,why would he only do it to this particular one? He actually is rubbing vents! The younger one is a male...he's turning green on his head,bronze on his chest and grey underneath.He also sounds raspy.I just thought it was weird because of the rubbing vent thing....(btw,the whole time the younger drake is resisting...and tries to get away.He has no injuries but it's rather annoying for him I'm sure! )

 

[Denninmi]

Yes, it's dominance behavior. And, just as in chickens, the strongest do it to the weakest, just to show everyone in the flock who is boss. Perhaps the other male was strong enough to fight the dominant drake off to the point the drake backed off a bit.

Its harmless overall, just what they do.

 

[NYRIR]

Really? Even the vent rubbing? So my original drake doesn't swing both ways

This is good news! Seriously though, I feel bad for the younger drake...he's a very calm,nice guy who is my favorite of the two younger ones.
It makes sense about him being weaker...he's a bit smaller of the 2 younger ones. Guess the nice guys really do finish last