Well, the word "teal" also refers to a dabbler (a type of duck). So given his colour choice, he could be called The Dabbler and his symbol could be the silhouette of a teal.
This would be a terrific pun if he were only a part-time superhero.
I'm guessing this probably won't be the choice you actually use, but it was the first thing that came to my mind.
Joy,
Lynn
