Pierus had 9 daughters and named each one after the muses. All the daughters could sing so they had a competition between them and the muses. The nymphs where the judges (controlled by Zeus, the muses' father). Pierus' daughters sang about how the Olympians fled from the Titans. The first muse sang, then Calliope sang about the greatness of the gods. The muses won. As punishment, Pierus' daughters were turned into magpies.