I think what would really be cool is if you had a triple evolve form showing more strengths in birds.
It would start out as a Hummingbird that is enraged, it'd be quick and have pretty decent attack.(Normal/Flying)
At level 18 it evolves into a Cardinal, due to the enragement, it is actually starting to turn red. This one is a little stronger and this is where it becomes a Fire/Flying type because of the red.
Finally, the rage of it at level 36 has settled and it has become more mature and becomes a Phoenix. These things are beautiful and it'd be awesome to see. (Fire/Flying as well)