During the day, go towards the Light Tower south of the Bazaar. As you do, you should see Parrow walking around – he’s quite a large man. Speak with him and you’ll learn that Orielle, his sister, went flying towards Fun Fun Island some time ago and has yet to return. Decide to help him, then start flying on your Loftwing.
As you go, go southwest towards Fun Fun Island. On the way there, keep an eye on the small islands you pass. On one, you’ll find a Loftwing on the island, with Orielle next to it. Apparently, her Loftwing got injured, and she lacks the medicine to heal it. Place a beacon or two here for future convenience, as you will come back in a few moments.
Return to Skyloft and speak with Parrow to receive a Bottle filled with the Mushroom Spores, the proper medicine for the Loftwing. Go back southwest to where Orielle is and speak with her. She’ll heal up her Loftwing and give you five Gratitude Crystals. Go back to Skyloft and speak with Parrow for the other five Gratitude Crystals.