Rattle

The Rattle is required for a side quest in Skyward Sword for 5 Gratitude Crystals. It is found in a bird's nest on top of the central windmill, next to the Bazaar. It is placed in your Collection page of your Gear.

Getting the Rattle
To get the rattle, you'll need Clawshots and the Gust Bellows.

Get out the Clawshots and use them on the vines growing on the floating island near the entrance of the Waterfall Cave.On that island, use the Clawshots again on the nearby vines on another anti gravity island and climb up from there. You should see a pool of water with water falling down to the bigger lake below once you get on that island. Walk around it and there should be some Blessed Butterflies gathering at the browner edge of the island. ( Optional : Play your Harp near that gathering of Blessed Butterflies and a Gossip Stone should appear. It will tell you you can reach the nest on the windmill below by skydiving to it. But what does it know? It's a stone. )On that browner ledge, jump off and tilt the Wii Remote towards the direction of the nest on top of the windmill, just like you did on the Wing Ceremony. Anyways, use your Gust Bellows to blow away the sand and you have completed the side quest once you return the rattle to Bertie, the potion improver at the Potion Shop in the morning, at night so he and the Unnamed Baby may finally go to sleep.