Stymphalian birds

In Greek mythology, Stymphalian birds were man-eating birds with wings of brass and sharp metallic feathers they could launch at their victims, and were pets of Ares, the god of war. Furthermore, their dung was highly toxic. They had migrated to Lake Stymphalia in Arcadia to escape a pack of wolves, and bred quickly and took over the countryside, destroying local crops and fruit trees. Ridding the land of these birds was one of Heracles' Twelve Labors, and some sources claim the Stymphalian birds were the same avians that attacked the Argonauts.

The Sixth Labor of Heracles

The forest around Lake Stymphalia was very dense, making it so dark as to impair vision. Athena and Hephaestus aided Heracles by forging for him huge bronze clappers (crotala), which scared the birds into flight. Hercules shot them down with his arrows, or according to other versions, a catapult. The birds that survived never returned to Greece.

Origin

When the sun is in the sign of Sagittarius, the constellations Lyra, Aquila the Eagle, and Cygnus the Swan, rise. (Lyra is now considered a lyre, but originally it was a vulture; eventually the vulture was imagined as holding a lyre, and eventually it became just a lyre). At this time of year (i.e. during Sagittarius) the evenings darken and the rain season in Greece starts, creating swampland from previously drier areas. Thus the bird constellations gained negative connotations. Sagittarius (the constellation) had various interpretations, especially as an archer but also as a rattle. In the later story, Heracles scared off the Stymphalian Birds (who lived in a swamp) with noise, and firing an arrow at them (the constellation Sagitta, an arrow, is aiming towards Aquila). The noise, archery, and sinister birds associated with the constellations may reflect the origin of the myth.