It was a very hot and humid August day so I had no plans to go outside until I saw a Great Egret in wonderful light foraging in shallow water. After taking a few egret phots, a Great Blue Heron swept in and chased him away.
What happened next was the real treat. Another Great Blue Heron flew in aggressively and the two Herons began a magnificent display. The newly arrived Great Blue Heron assumed this upright and spread wing posture.
Checking the internet for information about this behavior, I found this wonderful blog, featheredphotography.com, with some pictures of the same behaviour. The blog included information they credited to Cornell labs (requires a subscription with Cornell World of Birds):
The most spectacular display given by herons on the foraging grounds is the Upright and Spread Wing display that is given when two herons approach one another. The neck is nearly fully extended and tilted slightly over the back, the head and bill are held above the horizontal, and the wrists are drooped or held away from the body exposing the black shoulder patch of the adult. Sometimes the wing nearest the opponent is drooped lower than the opposite wing and the body plumes are erected. As opponents approach one another, the head and bill are raised closer to the vertical and the neck extended farther over the back.
The birds lowered their wings, but kept their heads and body plumes raised as their moved toward one another.
Their movements were measured and graceful, as they moved in a circle together and then as they slowly moved away from each other while keeping their heads and feathers raised.
