Beatrice as a Bluebird
Beatrice is a talking bluebird that accompanies Wirt and Gregory, giving little lines of advice to them every now and then. She is the tritagonist of the series, and is described by her voice actor to be somewhat of a grumpy bird. Beatrice is a daughter amongst many other children (presumably 10), who previously lived in the Old Grist Mill where the Woodsman ground Edelwood.
Her relationship with the two brothers evolve throughout the series, even though she isn't very openly caring. Most of the time, Wirt seems to believe that she doesn't enjoy the company of Gregory and himself.