This is Bird Note. When a northern saw wet owl spreads its wings, many birds can

see something our human eyes can't. The owl's flight feathers glow. It's invisible to

humans without the help of an ultraviolet black light which reveals a bright

magenta color.

Producing this otherworldly light is a trait called photoluminescence. While some bird

feathers simply reflect UV light, photoluminescence involves special pigments or

structures in the feathers that absorb UV and then release light of their own,

often in a different color. Some cases of luminous feathers have an apparent

purpose. For example, parakeets called budgerigars have glowing feathers on

their crowns and cheeks that may help them stand out to mates.

Over 50 species of parrots, as well as some two cans, have similar gleaming

ornaments. But for other birds, such as owls, we still don't have a good idea for

the reason behind the glow. The luminous owl wings do have a specific use for

biologists though. Scientists realized that they could estimate an owl's age

based on the pattern of luminescent color on the wings, which changes

predictably as birds grow and replace their feathers. It's a practical

application of a beautiful mystery.

For bird note, I'm Ariana Rimmel.