After collecting the 10 Phoenix Downs, go back down to the lower tracks and follow your partners. As they turn to the right, you need to take the left split because buried in the hill under the tracks is a cave with an out-of-work miner. A Power Source, Mind Source, and Tent may be acquired within this hidden area.
Note: Your score will be lowered if you do this. It's not nice to disturb baby birds.