I’m not sure ‘rival’ is the best description. These Herons get territorial about where they like to feed. What will happen is they chase each other, back and forth, trying to keep a space all to themselves (other species except Great Egrets are OK).

This bird was chasing another along the length of the main marsh.

They never meet up, just circling around squawking. Great Blues are more noise than anything else, except for big Egrets.

Great Blues and Great Egrets, not a good mix.