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Fluorescent pigments in the feathers of Long-eared Owls can only be seen by humans with the help of ultraviolet light. Photo credit: Chris Neri

While there is an astounding variety of physical differences in wildlife that humans can easily observe, new research from 91制片厂鈥檚  reveals that there is likely even more variation hidden from our perception. In a study recently published in , the researchers report their discovery of fluorescent pigments in the feathers of Long-eared Owls, that can only be seen by humans with the help of ultraviolet light.

The study, led by Emily Griffith, a PhD candidate in the  department, shows that fluorescent pigments in the feathers of Long-eared Owls can vary within a population and that variation gives clues as to why the owls have these special pigments.

To conduct the research, the team used a fluorometer 鈥� a device that measures fluorescence or light that is emitted after absorbing radiation such as UV light 鈥� to measure variation in the amount of fluorescent pigments in the feathers of Long-eared Owls migrating through the Upper Peninsula of Michigan in the spring of 2020.

A member of the research team holds a Long-eared Owl feather in their hand under the UV light. Photo credit: Chris Neri

鈥淲e are only beginning to describe fluorescent pigments in birds and other vertebrates,鈥� said Griffith. 鈥淎lthough describing what species they are present in is important, in order to understand what their function is we need to also describe how they vary within a species like the Long-eared Owl.鈥�

Griffith noted that in many bird species, pigments are used by males to attract females, which is why most people think of the males of many bird species as being more 鈥渃olorful鈥� than females. But the research team suspects that the function of these pigments is not necessarily related to sexual signaling.

鈥淥ur study shows that female Long-eared Owls have a much higher concentration of these pigments in their feathers, challenging a common misconception that colorful plumage is a 鈥榤ale鈥� trait,鈥� said Griffith. 鈥淢oreover, this trait doesn't follow a strict binary 鈥� the amount of fluorescent pigments in these owls exists on a spectrum where the amount of pigment is related to size, age and sex all together.鈥�

The Long-eared Owl. Photo credit: Chris Neri

The research team explained that fluorescent pigments have likely been used by animals for a long time, but technology has limited the study, or even acknowledgement of the pigments, until very recently. Griffith and her colleagues鈥� interest in the study stemmed from the fact that many owl researchers use these fluorescent feathers to age birds in the field, since the intensity of the fluorescent glow dissipates with time. Griffith added that researchers are just beginning to understand these 鈥渉idden鈥� traits in Long-eared Owls and other birds 鈥� what the fluorescence means, where it can be found, how it got there and why it鈥檚 there.

鈥淪o little is known about fluorescent pigments in bird feathers and owls aren鈥檛 the only ones with fluorescent pigments,鈥� said Griffith. 鈥淪o, it鈥檚 a really exciting time to be interested in studying bird plumage.鈥�

Read the full study here: .