Briar chickadoos are baby chickens that will eventually grow into a briar hen or more rarely, a roostro. Chickadoos of all varieties will never be eaten by slimes. Some believe this is because slimes are too kind-hearted to do such a thing. Others believe it's because chickadoos don't yet have enough meat on their bones.
Keep Briar Chickadoos in a safe place and they'll eventually grow into a Briar Hen or Roostro.