The Gods turned Procne into a swallow...
...and Tereus into a hawk...
He suffered for his crime by accidentally killing Procris with his spear...
Explanation:
In Greek mythology, Procne was the daughter of Athens' King Pandion. After Procne killed Itys and served his boiled remains to her husband Tereus, he tried to kill them upon realizing the fact.
It was then that Procne and her sister Philomela begged and prayed to the Gods to help them. The Gods answered their prayers, turning Procne into a swallow, Philomela transformed into a nightingale and Tereus became a hawk (or hoopoe).
Procne's niece, Procris, married Cephalus, who doubted her fidelity. He suffered for his crime by accidentally killing Procris with his javelin (spear). The spear had the capability of never missing its mark. Apparently, Cephalus had mistaken her sounds for that of an animal and had thrown the javelin in that direction.
