In wildlife, there is such a thing known as pecking order. I have observed and captured into images manifestations of this every time I go out and photograph birds at Ras Al Khor Wildlife Sanctuary.
Egrets and herons are always at it with the smaller one ending up being bullied and chased away.
But sometimes when it is about two of the same specie, one stands it’s ground and a fight occurs.
It is all about survival of the fittest….who get’s to catch fish and who ends up eating the fish.