Birds-of-Paradise Glow to Attract Mates, Adding a Flashy Element to Their Impressive Courtship Displays
Scientists find that 82 percent of birds-of-paradise species show biofluorescence, often on their feathers, throat or inner mouth
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Male birds-of-paradise have a lot of tools in their arsenal for attracting potential mates: bright feathers, elaborate dances and, according to new research, the ability to glow.
Scientists have found that 37 of the 45 species of the tropical forest birds are capable of biofluorescence—that is, their feathers absorb blue or ultraviolet (UV) light and emit it back out at lower, visible frequencies. Their findings were published in the journal Royal Society Open Science on Wednesday.
“It seems fitting that these flashy birds are likely signaling to each other in additional, flashy ways,” says Rene Martin, the lead author of the study and a biologist at the University of Nebraska-Lincoln, in a statement.
The team studied preserved museum specimens of birds-of-paradise using a specialized photography setup with UV and blue lights, then recorded the wavelengths and color of light emitted from the feathers. “What they’re doing is taking this UV color, which they can’t see, and re-emitting it at a wavelength that is actually visible to their eyes,” explains Martin to Jason Bittel at the New York Times. “In their case, it’s kind of a bright green and green-yellow color.”
“It may not have the effect of making something look different, but becoming brighter and more eye-catching,” she adds to the Guardian’s Nicola Davis.
Males were biofluorescent in areas that would be prominent during mating displays, such as the feathers on their head, neck, tail or belly, as well as the inner mouth, throat, bill and feet. Females also emitted a glow, primarily on the belly and chest.
Biofluorescence was more present in males than in females, which ties into the idea that the glowing feathers are used to attract mates. “Male birds-of-paradise often have these patches next to stark black [or] dark plumage, so the added effect of biofluorescence may aid in making these signal areas even brighter while being used during [courtship] displays,” Martin says to the Guardian.
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Three genera of the birds-of-paradise—Lycocorax, Manucodia and Phonygammus—showed no signs of biofluorescence. Martin tells the New York Times that those birds’ monogamous nature could be a possible explanation for their lack of glow, since they experience less competition between males. Those three genera must have lost the trait through evolution, she adds.
“Despite there being over 10,000 described avian species, with numerous studies that have documented their bright plumage, elaborate mating displays and excellent vision, surprisingly very few have investigated the presence of biofluorescence,” says study co-author John Sparks, an ichthyologist and curator at the American Museum of Natural History, in the statement.
Future research might even examine the animals in their outdoor, well-lit environment. “These birds in their natural habitat are going to be even more fluorescent than in museums,” Linda Reinhold, a zoologist at James Cook University in Australia who was not involved with the study, tells the New York Times.
The new research suggests scientists have more to learn about these already well-studied birds, Martin says to the Guardian. “Even a charismatic group like the birds-of-paradise that have been studied extensively can still offer new insights into avian vision, behavior and morphology.”
