Perhaps it’s the current trend for all banjo, fiddle and beard-wielding Americana bands, or maybe its promotor Moving On Music’s reputation as a purveyor of musical excellence that’s pulled them in, but whatever the reason it’s a full house in the Black Box for Pennsylvanian bluegrass trio The Stray Birds. Maya de Virtry, Oliver Craven and Charlie Muench played this same room just over a year ago though tonight, judging by the paltry show of hands in response to Craven’s “who was here last time?” survey,  it seems like a new audience is here to catch one of the hottest…