Looking for a book similar to those by Robin jarvis?

I remember reading a book, similar to the works of the venerable Robin Jarvis. It was part one of (x number), I know because I am trying to finish off the collection.

It dealt with animals that could change aspects of themselves, animorphing under the guidance of a master. I think the animals were mice (which leads me to the Robin Jarvis connection). In this first novel of many, a mouse pupil becomes better than the master. The master became jealous of this pupil, and found out that the pupil was better at morphing than himself. If it helps, this pupil was adept at changing into a blackbird, which was one of the hardest animals to master.

Well, it turns out that this pupil was only better than the master by stealing shavings off the ancient trees of his ancestors, a morally wrong action to take. This master goes off to reveal his pupils secret. On the way to the village however, a group of "undead?" find this master, and the once "never put a foot wrong master", sells out his tribe,