Birdie Rattle

The Birdie Rattle is a pet-summoning item that can be purchased from the Traveling Merchant for. It is used to summon the Lil' Harpy pet.

The Lil' Harpy, when summoned, will fly above and behind the player, and will behave similar to the Zephyr Fish, continually flying around and looking side to side. It will never land, and can fly through blocks.

Trivia

 * The tooltip mentions a cockatiel, which is a member of the cockatoo family.