Biofluorescence is used by birds of paradise to attract mates
A recent study has uncovered that biofluorescence is widespread among birds-of-paradise, a group of tropical birds renowned for their elaborate courtship dances and vividly colored plumage. Researchers found that 37 out of 45 known species exhibit this hidden glow, which appears more pronounced in males and could play a role in attracting mates or asserting dominance. Conducted by scientists from the American Museum of Natural History (AMNH) and the University of Nebraska-Lincoln, the study sheds new light on the visual complexity of these already dazzling creatures.
Birds-of-paradise, found in New Guinea, Indonesia, and parts of eastern Australia, have long fascinated scientists with their unique mating behaviors, intricate feather displays, and acrobatic performances. The discovery of biofluorescence adds another layer to their courtship rituals, revealing a hidden spectrum of communication previously unnoticed by the human eye. Biofluorescence occurs when an organism absorbs light at one wavelength and emits it at another, creating a luminous effect that is only visible under certain lighting conditions. This fluorescence had remained undetected until now, as it requires specialized instruments to observe.
The study was inspired by an observation made over a decade ago when Museum Curator John Sparks, originally an ichthyologist, noticed that some bird specimens, including birds-of-paradise, emitted a green-yellow glow under specific wavelengths of light. This unexpected finding prompted further investigation, leading to the realization that biofluorescence is not just a rare occurrence but a common feature across numerous species in this bird group. By using ultraviolet light, researchers confirmed that these birds not only glow under blue wavelengths but also emit a particularly strong fluorescence under UV exposure. This effect is most noticeable on male plumage, especially on body parts essential for courtship displays, such as the head, neck, and belly, as well as inside the mouth and along the bill lining. While females also exhibit fluorescence, it is less intense and primarily visible on the chest and belly.
Scientists believe that the bright and varied light conditions near the equator, where these birds live, may enhance the visibility of their biofluorescent signals. Since birds-of-paradise are known for their exceptional vision and complex visual displays, the presence of fluorescence likely plays a role in their social and mating interactions. Prior research on closely related species suggests that these birds have eye pigments aligned with the fluorescence peaks identified in this study, meaning they can likely perceive and interpret these glowing patches in ways humans cannot. When a male performs its elaborate courtship routine, these biofluorescent highlights may act like a hidden spotlight, making his movements and feathers appear even more striking against the darker tones of his plumage. This could serve as an additional cue to attract a female’s attention or assert dominance among rivals.
Despite extensive research on birds-of-paradise regarding behavior and coloration, the discovery of fluorescence at this scale suggests that birds may have even more sophisticated communication methods than previously thought. The presence of glowing patches across multiple species raises the possibility that biofluorescence could be more widespread in the avian world, particularly among species known for their striking colors and elaborate displays. Researchers now aim to explore how environmental factors such as canopy density, seasonal light variations, and habitat changes influence these glowing signals. Additionally, understanding how birds-of-paradise perceive and respond to fluorescence could offer new insights into the evolution of avian sexual selection and signaling mechanisms.
This research challenges existing ideas about visual communication in birds and opens the door to further discoveries. As imaging technology advances, scientists may uncover that biofluorescence is far more common across bird species than previously imagined, adding a new dimension to the already intricate world of avian displays.
