In a typical situation, a blue heron and a great egret will look for practically any excuse to squabble and start an argument.
Usually, as in the case here, it’s over who is the rightful owner of a particular fishing area.
It’s not even that it’s a terrific fishing spot worth fighting over, it’s just that one bird doesn’t want the other one there on principle.
This behavior has likely been going on for thousands of years and continues on to this day. Birds will be birds. 🙂