Positively radiant Flashy exotic birds can actually glow in the dark The birds, known for their showy displays, look even more colorful than we thought. Elizabeth Rayne Feb 23, 2025 7:20 am | 2 Credit: TeeJe Credit: TeeJe Story textSizeSmallStandardLargeWidth *StandardWideLinksStandardOrange* Subscribers only Learn moreFound in the forests of Papua New Guinea, Indonesia, and Eastern Australia, birds of paradise are famous for flashy feathers and unusually shaped ornaments, which set the standard for haute couture among birds. Many use these feathers for flamboyant mating displays in which they shape-shift into otherworldly forms.As if this didnt attract enough attention, weve now learned that they also glow in the dark.Biofluorescent organisms are everywhere, from mushrooms to fish to reptiles and amphibians, but few birds have been identified as having glowing feathers. This is why biologist Rene Martin of the University of Nebraska-Lincoln wanted to investigate. She and her team studied a treasure trove of specimens at the American Museum of Natural History, which have been collected since the 1800s, and found that 37 of the 45 known species of birds of paradise have feathers that fluoresce.The glow factor of birds of paradise is apparently important for mating displays. Despite biofluorescence being especially prominent in males, attracting a mate might not be all it is useful for, as these birds might also use it to signal to each other in other ways and sometimes even for camouflage among the light and shadows.The current very limited number of studies reporting fluorescence in birds suggests this phenomenon has not been thoroughly investigated, the researchers said in a study that was recently published in Royal Society Open Science.Glow-upHow do they get that glow? Biofluorescence is a phenomenon that happens when shorter, high-energy wavelengths of light, meaning UV, violet, and blue, are absorbed by an organism. The energy then gets re-emitted at longer, lower-energy wavelengthsgreens, yellows, oranges, and reds. The feathers of birds of paradise contain fluorophores, molecules that undergo biofluorescence. Specialized filters in the light-sensitive cells of their eyes make their visual system more sensitive to biofluorescence.To find out just how many species of these birds fluoresce, Martin screened specimens of adult males and females in a dark room by shining blue and ultraviolet light on them. Most species ended up glowing green or yellow-green. Males had the most biofluorescent plumage, which was observed on the head, neck, chest, and abdomen. Even the skin on their feet and the insides of their mouths would fluoresce in blue and UV light.Females had fewer biofluorescent feathers, usually on the chest and abdomen. Birds of paradise are highly sexually dimorphic, meaning males and females look very distinct, so this isnt a surprise. This made sense to Martin because it is thought that biofluorecence in these birds evolved largely through sexual selection, with the males that can show off more fluorescent feathers being more likely to land a mate.Biofluorescence also depends on habitat. Most birds of paradise live high in the forest canopy, while some dwell closer to the ground. The amount of high-energy radiation that filters in through the foliage can vary greatly between habitats, some of which are heavily shaded by leafy canopies, while others are more open and allow more sunlight in.ShowoffHow the birds move can also affect the way their fluorescence shows up. Direct light from larger gaps in the canopy makes it more obvious, while incident light that does not hit the feathers directly has a more subtle effect. Sometimes the bird can change its degree of fluorescence just by moving into areas with more or less light. Females tend to use this for camouflage, while males use it to show off.Take the mating display of the Western parotia (Parotia sefilata). The male will clear an area on the forest floor, which the researchers think may be a way to reduce visual background noise so his plumage stands out even more. He can even change his eye color from blue to a striking yellow by contracting his bicolored irises. He dances and flashes his fluorescent patches until the female decides whether he has enticed her.Something that is immediately noticeable about the Western parotia and many other birds of paradise is that most of their feathers are a shade of black so dark and impenetrable that Martin and her team call it super black. It is thought to be the ultimate contrast to their brighter colors generated by bioluminescence. Species without these super black feathers were found to be lacking in biofluorescence.While it may be hard not to notice the bizarre beauty of birds of paradise, the researchers wonder whether biofluorescence may be a more widespread phenomenon among birds. There are a handful of parrot, owl, nightjar, penguin, and puffin species that are known to have biofuorescent feathers or patches of skin.But not all biofluorescence necessarily comes associated with ultra-dark feathers. "The presence of white or light-colored feathers (i.e., that may contain fluorophores that result in fluorescence) in the majority of avian lineages indicates that fluorescence may be far more widespread in birds than what has been reported in the literature to date, the researchers said in the same study.It is possible. The Moluccan cockatoo, which is mostly white except for the coral feathers in its crest, is endemic to the Moluccas, islands off the east coast of Indonesia that are also home to some species of birds of paradise. Whether this parrot species is biofluorescent is unknown for now, but it might be a good species to test the researchers hypothesis.Royal Society Open Science, 2025. DOI: 10.1098/rsos.241905Elizabeth Rayne Elizabeth Rayne is a creature who writes. Her work has appeared on SYFY WIRE, Space.com, Live Science, Grunge, Den of Geek, and Forbidden Futures. She lurks right outside New York City with her parrot, Lestat. When not writing, she is either shapeshifting, drawing, or cosplaying as a character nobody has ever heard of. Follow her on Threads and Instagram @quothravenrayne. 2 Comments