The great hero set off on his journey thinking this should be quite an easy task to accomplish, but on reaching Lake Stymphalus Heracles realized this was not so. The forest in which the birds would roost was very dense, and so dark it was hard to see anything. Heracles, trying to think of a way in which to drive the birds from their hiding place, was approached by Athena, goddess of invention, and also a protectress of Heracles. It was she, with the help of Hephaestus, the smith-god, who devised a way to drive the birds from the forest.
On Athena's instruction, Hephaestus fashioned a huge pair of bronze clappers, to startle the birds into flight. Heracles, with his great strength, smashed the clappers together, which drove the birds to flight, and then, as the birds came into sight he shot them down with his deadly arrows. (there is evidence shown on a black-figure amphora, which depicts Heracles shooting down the birds with a catapult). Those that escaped the deadly arrows (or catapult) kept on flying ,and never returned again to Greece.