Hello, Jay! So, that's actually counts as a Siren in the Multiverse? So far we've seen bird-people, water maidens and even the ripoff of Ursula from "The Little Mermaid". What they have in common? Why are they all classified as such?
A siren is about bring a sea spirit with an alluring call, not a specific form. The most common we’ve seen are the Theros and Ixalan ones, which are based on a certain kind of siren myth (the winged one).
OK so they are all based on the actual history of siren mythology in Europe.
Sirens are first seen in the Odyssey, where Homer never describes them physically but instead focuses on their song. This song is seductive not for any reason of sex appeal, but because the sirens know everything that has ever happened. The allure of the sirens is secret information, which is why Odysseus gets lashed to the mast to he can hear their song.
Later Greek depictions show them as bird people (potential Egyptian influence), so Magic's many depictions of sirens as beople (bird people) is rooted in these original Greek works:
Obviously, they are beople on Theros because that is their culture of origin, but they're also beople on Ixalan because merfolk already have the feople (fish people) thing covered.
Some feople sirens do exist in ancient Greek art, as they are beings always associated with the ocean. But the popularized image of sirens as seductive mermaids is from medieval bestiaries and a result of Christian Nonsense (TM) about women. This image gets reinforced again and again as European sailing quests go global, and now the modern conception of the siren is heavily entangled with mermaid folklore.
There are also medieval depictions that have fish tails AND wings, which is neat! Ultimately, they're two different depictions of a creature that was undescribed in its original stories. Over time, without a wiki to reference, lots of stories got remixed, and different cultures highlighted different aspects of the siren in ways that were resonant with the people redepicting them in their respective times.
Art and culture are messy and complicated when stretched accross millennia! It's fun!
