I'm not sure if it is a territorial display. As I understand it the horn on the bill doesn't denote sex. The "horn" is shed after the birds have mated and laid eggs.
It was interesting watching the birds herd fish towards a spillway where they would start trying to catch them. They would let the current move them away and start again.
There was only the occasional pushing match to be in the front of the group when they got to the spillway. When this photo was taken they weren't actively feeding.
I thought the lines were nicely aligned on this one but I caught about three frames of this aggression.
