Lookin' good. I'd expand it out to include the feathers of magical creatures as well:
Consume Magic (Su): A lesser plumazotl advances in hit dice by absorbing magic items into its body. The magic item to be consumed must have feathers or be associated with feathers, such as a feather token or a magic arrow. For every 1000 gp? of magic items that the lesser plumazotl consumes, it gains one hit die; when it reaches 6 hit dice, it metamorphoses into a greater plumazotl.
Additionally, a lesser plumazotl can consume the feathers from magical beasts and outsiders. The lesser plumazotl gains 1 Hit Die for every 5? HD the original creature possessed. A lesser plumazotl may only gain this benefit from a specific creature once, even if additional feathers are consumed.