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While many bird species are known for their vibrant colors, birds-of-paradise stand out with their flamboyant hues of emerald, lemon, cobalt, and ruby. Recent research has unveiled that these remarkable birds are also sending hidden color signals that are invisible to the human eye. A new study published in the journal Royal Society Open Science on February 12 reported that the plumage and body parts of birds-of-paradise appear to glow under blue and ultraviolet (UV) light, showcasing bright green or yellow-green colors.
Living organisms emit light through bioluminescence or biofluorescence. Bioluminescence, seen in fireflies, involves a chemical reaction with luciferin and luciferase molecules. Biofluorescent creatures absorb high-energy wavelengths like UV, violet, or blue light and then emit light at a lower energy wavelength. Researchers have identified biofluorescence in 37 out of the 45 known species of birds-of-paradise, which are found in remote tropical forests and woodland habitats of Papua New Guinea, eastern Indonesia, and parts of Australia. When illuminated by blue and UV light, these birds display white and bright yellow plumage that may serve purposes like territorial signaling or attracting mates.
While many bird species have excellent color vision, little is known about the vision capabilities of birds-of-paradise. Closely related lineages with sensitive vision to violet light suggest that birds-of-paradise may have similar abilities. The ability to fluoresce may play a crucial role in their visual communication, shining brightly in the dark for specific purposes such as attracting potential mates or asserting dominance.
Dr. Jennifer Lamb, an associate professor of biology at St. Cloud State University, commended the study’s comprehensive approach in exploring biofluorescence in birds-of-paradise and their relatives. She highlighted the significance of understanding visual signals that are not perceivable to the human eye as a potentially overlooked aspect of communication among diverse species.
Lead study author Dr. Rene Martin pointed out that the discovery of biofluorescence in birds-of-paradise adds a new dimension to our understanding of their visual communication strategies. The findings suggest that such visual signaling mechanisms may be more widespread in nature than previously thought, emphasizing the importance of further research in this area.
Martin, a fellow fish biologist and an assistant professor at the University of Nebraska–Lincoln, led him to question the prevalence of this trait in other animals. Sparks had access to a wide range of bird specimens at AMNH. A preliminary examination of the museum’s ornithology collection with a blue light confirmed his suspicions, revealing fluorescent traces in birds-of-paradise, as noted by Martin. The investigation deepened when Martin joined the museum as a postdoctoral researcher in 2023, along with Sparks and study coauthor Emily Carr, a doctoral student at the Richard Gilder Graduate School.
Together, they revisited the birds-of-paradise specimens in the museum’s drawers. Martin used high-powered blue and UV flashlights to meticulously search through the collection while wearing special goggles that filtered out the blue light, revealing only the fluorescence emitted by the birds-of-paradise. The researchers then photographed the birds in a lightless room and measured their light emissions, discovering that fluorescence appeared in various body parts across different species, such as their bellies, chests, heads, and necks. Some species exhibited long glowing plumes, shimmering bills, or sparkling spots in their mouths.
The presence of biofluorescence in birds-of-paradise fascinated the scientists, especially how the fluorescence interacted with the birds’ darkly pigmented feathers and ultra-black feathers that absorbed light. The study shed light on biofluorescence in a fraction of bird species, suggesting potential uses in communication and reproductive displays, particularly in parrots and birds-of-paradise.
Biofluorescence, once thought to be limited to certain bird groups, was found in 37 out of 45 known species of birds-of-paradise inhabiting remote tropical forests. Recent discoveries of biofluorescence in various animal groups, including fish, salamanders, sea turtles, mammals, and marsupials, indicate a broader occurrence than previously assumed. Understanding biofluorescence could offer insights into evolution and potentially contribute to medical or technological advancements.
Studies are being conducted to shed light on the various stages of embryological development and to unveil the progression of cancers and different types of cells. “It is highly probable that if biofluorescence is observed across multiple branches of the tree of life, it carries significant implications for the organisms showcasing this trait,” remarked Martin. “Whether it is seen in birds-of-paradise possibly utilizing it for signaling purposes or in another organism using it for camouflage, it represents an additional adaptation that organisms are evolving to enhance their chances of survival and reproduction.” Mindy Weisberger, a science writer and media producer, has contributed her work to publications such as Live Science, Scientific American, and How It Works magazine. For the latest CNN news and updates, sign up for an account at CNN.com.
