That's a pretty good idea. I've trash bagged a few bird houses that were infested with 'em and gassed 'em inside before. Worked pretty good.
Back to the herons. I've been to San Antonio and found it a pretty sociable place. Why the herons there would be anti-social I really don't know, but once they cross the Red River and head our way they seem to flock just fine when there's something to snack on...