Owl feathers can glow pink or magenta under ultraviolet (UV) light.

The glow comes from porphyrins, pigments naturally present in some owl feathers. When exposed to UV light, these pigments fluoresce, producing a striking pink or reddish glow.

As feathers age and wear, their porphyrins gradually break down, causing the intensity of their fluorescence to decrease. Researchers can use these differences to identify newly grown feathers and distinguish different generations of feathers across an owl’s wing.

These fluorescence patterns can also provide clues about a bird’s age by revealing its molt history.

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