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 him and Gregory.
She is a small bluebird with a grey-colored head, a red breast, and a white underbelly. Her wings are blue with darker blue tips. As a human, she has red hair put into a sort of abstract bun and wears a blue dress. She appears to be a teenager like Wirt although her age is never specified.
Beatrice is portrayed as a very tough girl. She is emotionally closed off and doesn't easily convey or show affection. She was, perhaps, a very angry or aggressive child, as she had thrown a rock at a bluebird, which then cursed her and her whole family. After her transformation, Beatrice was ridden with guilt and would do anything to transform her family back into humans. She thinks her family resents her because of her actions, when in reality they miss her and love her dearly. She develops a friendship with Wirt and Greg, even through she is mostly nagging them and pointing out their flaws. Beatrice is later revealed to be very kind, caring, and supportive, as shown in Mad Love when she tells Wirt how she became a bird, and her determination to cure her family. Her kind nature is also evident in Lullaby in Frogland when she supports Wirt in his bassoon playing. Even though her intentions are good, her pride and stubbornness often get her in trouble.
One day, Beatrice threw a rock at a bluebird, which consequently cursed her along with the rest of her family. Instead of facing them and owning up to her misdeed, Beatrice decided to flee home. She eventually made an agreement with Adelaide of the Pasture, which tasked the young girl to find a child in exchange for a pair of scissors that would revert her family back to human form.
On the night Wirt and Greg wandered into the woods, Beatrice encountered the brothers briefly, but fled when the Woodsman approached them. The following morning, she became entangled in a rose bush and was set free by Wirt and Greg as they happened to be walking down a nearby trail. Beatrice decided to follow the brothers to a village called Pottsfield, planning to offer them to Adelaide in order to allegedly help them.
Beatrice accompanied Wirt and Greg into a farmhouse and was the first to be disturbed by the festivities of the eccentric, pumpkin-wearing townsfolk. After the brothers were sent to do a few hours of manual labor by Enoch, Beatrice gave into Wirt's pleas to help them escape when Greg discovered a skeleton while digging holes. Once the three escaped, they continued on to Adelaide.
The three stopped at a colonial tavern one night in order to ask for directions, but Beatrice was immediately run out by the proprietor for fear of bad luck. She sat outside in the rain attempting to converse with a horse in the tavern's shed, but gave up and eventually flew over to the Woodsman who she heard nearby in order to get directions on her own. Beatrice screamed right before she was rendered unconscious, and was rescued by Wirt.
Beatrice, Wirt and Greg eventually made their way into the estate of Quincy Endicott. Here, they joined him for dinner while Beatrice convinced the confused baron that Wirt and Greg were his nephews. Beatrice urged Wirt to join her in finding loose change, making a mess of the parlor. After mistaking the sound of a peacock pecking against the window for Endicott returning, Beatrice and Wirt hid and became trapped in an armoire.
In Lullaby in Frogland, she attempts to convince Wirt to not go to Adelaide's house. While the brothers sleep, she flies alone to the witch's hut to try to convince Adelaide to not take the brothers, and instead offers herself. It becomes evident that Beatrice didn't know Adelaide's true intentions with the boys. She is astounded when Adelaide says that she needs a "child servant", having believed that the old witch simply needed some yard work done.
Wirt and Greg soon appear at Adelaide's hut, having followed Beatrice, and after Wirt has discovered Adelaide's plan, he believes that Beatrice has betrayed him and Gregory. Wirt then steals the scissors that were intended to turn Beatrice's family back into humans. Beatrice is left alone and regretful as Wirt angrily leaves with Gregory, and soon searches for the two boys.
After Greg saved Wirt from being The beast's next victim, Beatrice had found Wirt who almost drowned, took him to her family and went on her own to find Greg. After awakening from Beatrice's family's tree home, he eventually found Beatrice and the two looked for Greg. The two find both Greg who is about to become an edele wood and the Beast's dark lantern. The Beast tried to make a deal with Wirt, promising that he could place Greg's soul inside his lantern and he would live on as long as the lantern stays lit. Wirt rejects his offer and notes that the Beast is so obsessed with keeping the lantern lit, it was as if his own soul was inside the Lantern. As Wirt threatens to blow out the flame inside the lantern and The beast immediately screams "No", proving Wirt's suspicions true. Wirt gives The Woodsman back the lantern seeing it as his problems and takes him and his brother home. Before leaving, Wirt gives Beatrice the magical scissors that will turn her and her family human again.As the story ends, it shows that Beatrice and her family are human again and have moved back to their home. Beatrice's mother tells her to eat her meal she calls "dirt". Beatrice asks her mom to stop calling that and her mother says what was she going to do about it, jokingly asking of she was going to turn them all to blue birds again and her family laughs.
- Beatrice seems to be an eastern bluebird (Sialia sialis).
- Her voice actor is Melanie Lynskey.
- As a human, she resembles Wendy Darling from Disney's Peter Pan (1953)