(Στυμφαλίδες), the celebrated rapacious birds near the Stymphalian lake in Arcadia, whence they were driven by Heracles and compelled to take refuge in the island of Aretias in the Euxine, where they were afterwards found by the Argonauts. They are described in different ways, but most commonly as voracious birds of prey, which attacked even men, and which were armed with brazen wings, from which they could shoot out their feathers like arrows. (Apollod. 2.5.2; Paus. 8.22.4; Hygin. Fab. 30 ; Schol. ad Apollon. Rhod. 2.1053.) They are said to have been brought up by Ares. (Serv. ad Aen. 8.300.) According to Mnaseas (apud Schol. ad Apollon. Rhod. 2.1054), they were not birds, but women and daughters of Stymphalus and Ornis, and were killed by Heracles because they did not receive him hospitably. In the temple of the Stymphalian Artemis, however, they were represented as birds, and behind the temple there were white marble statues of maidens with birds' feet. (Paus. 8.22.5.)
[L.S]A Dictionary of Greek and Roman biography and mythology
Smith, William
A Dictionary of Greek and Roman biography and mythology. William Smith, LLD, ed. 1890