Who is Jack from A Year in the Maine Woods and what is their importance?

Jack is Heinrich's raven. He captures Jack at the beginning of the book and take him with on the drive to Maine. Jack is great company, and Heinrich considers him his traveling companion.

After arriving at the cabin, Jack begins to progress from an adolescent to an adult. Heinrich observes Jack's playful behavior, and eventually has to deal with his budding independence. As a raven expert, Henrich includes a variety of stories about his experiences with Jack.