Here’s what you’ll learn when you read this story:

• The world is filled with cryptozoological mysteries with no discernible answer, like Bigfoot or the Loch Ness Monster.
• On the island of Sri Lanka, there’s a longstanding legend of a “Devil Bird,” or Ulama, who haunts the jungle and whose human-like shriek is an ill omen.
• In more recent times, experts have tied the folklore legend to the spot-bellied eagle-owl but others argue that other birds, such as the Oriental Honey Buzzard or the Changeable Hawk Eagle, could be the source of the myth.

Creatures from the world of cryptozoology (the search for legendary creatures such as Bigfoot or the Loch Ness Monster) rarely transition from myth to reality—rarely, but not never.

Throughout the 18th and 19th centuries, for example, western scientists laughed at the idea of an elusive “African unicorn,” one the Indigenous Congolese called “o’api.” Those dismissive chuckles were roundly silenced in 1900 when British explorer Harry Johnston sent hide samples of what we now call the okapi to the Zoological Society of London. For 15 years, the now-dissolved International Society of Cryptozoology used the okapi as its mascot of sorts.

Of course, the “o’api” is far from the only puzzling cryptozoological mystery in the world, and one of the most enduring can be found on the South Asian island of Sri Lanka—once known as Ceylon—where, for more than a century, locals have lived in fear of the Ulama, or Devil Bird.

“Most people who visited the island of Ceylon and penetrated into its jungle…have heard the cry of the Devil Bird,” an article in Sydney’s Sunday Times reported back in 1907. “This awe-inspiring sound resembles nothing so much as the scream of a human being undergoing the most terrible torture.”

The legend associated with the Ulama is as blood-curdling as its human-like scream. According to legend, a jealous husband doubting his wife’s fidelity killed their infant son, cooked him, and served it to his unknowing wife, who, upon discovering a finger left in the dish, fled into the night in a frenzy and transformed into the Ulama. According to a folklore account published in the journal Nature back in 1887, the Devil Bird’s screams “represent the agonized cries of the bereaved mother when she left her husband’s house.” For centuries, the cries of the Devil Bird were considered a bad omen throughout Sri Lanka whenever it was heard.

While certainly a frightening origin story, naturalists and scientists have searched for a more mundane explanation, much like the discovery of the okapi (which is distinctly not a unicorn). Even back in 1907, the Sunday Times reported that the most likely avian inspiration behind the Devil Owl was the brown wood owl (Strix leptogrammica), a species that’s found across South Asia.

However, more recent investigations have found that the call of the spot-bellied eagle-owl (Ketupa nipalensis) may be what locals have been mistaking for a horrifying avian demon. The sixth largest owl in the world, the spot-bellied eagle-owl, also known as the forest eagle-owl, sports impressive large ear tufts, giving its face an all-around demonic appearance. The book The Far-Off Things by Sri Lankan physician and author Richard Spittel mentions two other possible candidates, including the Changeable Hawk Eagle (Nisaetus cirrhatus ceylanensis) or the Oriental Honey Buzzard (Pernis ptilorhynchus). While the exact real-life version of the Devil Bird is up for debate, it seems all but certain that those haunting cries come from an avian friend who’s already well-known to science.