It sounds like the name for a boutique airline. Blue Heron is, in fact, the handle for yet another crack Boston vocal ensemble with an avian name currently giving the Brits a run for their money. (Limelight readers will already be acquainted with the excellent and versatile group Skylark that also hails from the land of the tea party and clam chowder.) Blue Heron has the distinction of being the first North American ensemble to win the Gramophone Early Music award in its 41-year history.