Rooks are ravens, a larger specie of the crow family. The term rook is used in Britain, and I always wonder what if anything that has to do with chess rooks. I don't know that yet, but I do know that the Tower of London grounds house some whopping rooks. Their wings are trimmed to keep them handy, for there's a legend that if the ravens desert the Tower, England will fall.
Pretty good reason for keeping them as pets, I'd say.
I saw them myself twelve years ago, and they are not exactly hurting for rook chow. They are lovely in their satiny blacker than black way (that color is fuligin, if you're a Gene Wolfe fan). Would you like to learn more about them? Here you go.