Pick up the 3 "Super Cucco's" in Lon Lon Ranch. (As a child)
As a child, Collect all the Cucco's in Karakiro Village and throw them into the Chicken Fence. Then talk to the lady.
Get it from the bottom of Lake Hylia. It has Ruto's letter in it.
As an adult, find the 10 big Poes. You'll encounter them in different areas of Hyrule Field (only on horseback). Shoot them twice and return them to the lady in the first house when you enter Hyrule.