The stymphalis is a man-eating bird with a beak of bronze, sharp metallic feathers it can launch at its victims, and poisonous dung. According to the Greek legend of the Labors of Hercules, he destroyed the birds with poisoned arrows.

The stymphalis appears in some medieval encyclopedias. It was sometimes confused with the harpy (strophalides, strophades).

The seronfalide is a bird that appears in the Liber floridus of Lambert of Saint-Omer. It has a one line description: Seronfalides aves in insulis habitant (Seronfalides are birds that live on islands). No other description of it is provided. This bird is most likely the stymphalis.