The silbaco is a bird with a strange call and whose appearance is said to be so shocking that those unfortunate enough to see it can lose their hearing or suffer heart attacks. Initially it sounds like it's whistling, but as it comes closer, it turns into a heart-stopping screech. The tale claims there was once a man, a very hard-working one, who had a wife and two children. He earned a living by selling wood, and was prosperous, but one day he began to feel ill and began to suffer small transformations until he finally turned into a very strange creature, half man, half bird.

Scared, his wife asked for the local priest for help. The priest did all he could, but nothing could stop Pedro’s metamorphosis: he became a bird, an ugly one, all black, and with a high-pitched call, which villagers named Silbaco, as Pedro had been known for his penchant for whistling. The unfortunate man, now a bird, fled to the forest, never to be seen again. On dark nights, his call could be heard, but he was rarely ever seen.