Descripción del sitio
The forest around Lake Stymphalus was very dense and too dark to see much. Athena and Hephaestus helped Heracles kill the birds as the sixth of his Twelve Labours. Hephaestus made huge bronze clappers to drive the birds into flight, and Heracles shot them with his arrows or a catapult. The birds that survived never returned to Greece.
http://en.wikipedia.org/wiki/Stymphalian_Birds