Both Pliny the Elder (1st century A.D) and Isidore of Seville (7th century A.D) wrote down note of the Hercinia. Named after its home in the Hercynian Forest (currently half of this ancient forest is known as the Black Forest) in Germany, this bird had a noticeable trait. The Hercinia’s feathers would glow brightly in the night, able to be used by travelers to keep paths lit. Often times in ancient bestiaries, drawings of this bird would contain gold leaf to represent its glow.

Isidore of Seville wrote, “Their feathers sparkle so much in the shade that, however dark the night is with thick shadows, these feathers, when placed on the ground, give off light that helps to mark the way, and the sign of the glittering feathers makes clear the direction of the path.”