 With the story of Philomela, most of the variations concern which sister became the nightingale or the swallow, and into what type of bird Tereus was transformed.Since Ovid's "Metamorphoses", it has been generally accepted that Procne was transformed into a nightingale, and Philomela into a swallow.The description of Tereus as an "epops" has generally been translated as a hoopoe (scientific name