I had assumed this was a young Black-crowned while following him. The Black-crowns have been setting up house in the big rookery, and now the smaller one. I gave it no thought since he was traveling along near them.
This bird has a different beak and is taller. Now I need to move around both rookeries to see who is living where. There must be more since I rarely see them alone.
BTW, they look nothing like an adult which is blue, white, and black.