Stymphalian Birds

Stymphalian Birds are a species of monstrous pigeon-like birds.

History
In Greek Mythology, Heracles' sixth labor was to beat the Stymphalian birds. He did it by using brass bells to scare them away.

The Sea of Monsters
Stymphalian birds attack Camp Half-Blood during a chariot race. Percy and Annabeth used Chiron's music from a portable stereo to confuse the birds so Apollo's cabin could shoot them down. The reason they could enter the camp's borders was because of Thalia's tree dying. Tantalus apparently then cooked and served them for the winning camper's (which was Clarisse) prize-dinner.

Abilities
Stymphalian birds have sharp Celestial Bronze beaks that can tear through flesh. They also have the ability to use their feathers like arrows, being able to shoot them down at their prey from above.