Harpy

The Harpy is a flying enemy that spawns at high altitudes, typically above the height of Floating Island. It uses the Bat AI, and fires Harpy Feathers.

Harpies can spawn at any time, day or night. Up to 7 Harpies can exist on screen during the day, 10 at night, and 15 during a Blood Moon.

When you see them, that means that there is a chance a Wyvern could spawn.

History
Harpie Harpy Harpy Гарпия