Birds-of-paradise are sending secret color signals invisible to human eyes, scientists say

Many types of birds — such as hummingbirds, peacocks and parrots — are vividly colorful, but birds-of-paradise are especially flamboyant with hues of emerald, lemon, cobalt and ruby. Now, research has revealed these stunning birds are also sending secret color signals that are invisible to human eyes.

Plumage and body parts of birds-of-paradise glow in certain areas when viewed under blue and ultraviolet, or UV, light, appearing bright green or yellow-green, scientists reported in a new study published February 12 in the journal Royal Society Open Science.

Living organisms produce light in two ways: русское порно жесток bioluminescence and biofluorescence. Bioluminescence (the light produced by fireflies, for instance) requires a chemical reaction involving the molecules luciferin and luciferase. Biofluorescent creatures generate their glow with structures that absorb high-energy wavelengths of light, such as UV, violet or blue, then emit the light in a lower-energy wavelength.

Researchers described biofluorescence in 37 of the 45 known species of birds-of-paradise, found only in remote tropical forests and woodland habitats of Papua New Guinea, eastern Indonesia and parts of Australia. Illuminated by blue and UV light, the birds’ white and bright yellow plumage broadcasts colors that may be used in territorial disputes or for finding mates, according to the study.

Birds are known for their exceptional color vision, and many types of birds — among them pigeons, turkeys, ducks and geese — can see in the UV spectrum. Little is known about the vision of birds-of-paradise. However, some closely related lineages, including the Corvus genus (crows and ravens), the Rhipidura genus (fantails), and the Pica genus (a type of magpie) are known to have vision that’s sensitive to wavelengths of violet light. For such birds, fluorescent markings would shine like a beacon in the dark, the study authors wrote.

"The study is well-designed, in terms of looking across the diversity of the birds-of-paradise group as well as at some of their close relatives," said Dr. Jennifer Lamb, an associate professor of biology at St. Cloud State University in Minnesota. Lamb, who studies biofluorescence in amphibians and reptiles, was not involved in the research.

"What’s really interesting about biofluorescence is that even though it is a visual signal, or it can be a visual signal, it’s still been relatively understudied in a lot of different groups," Lamb said. "So we’ve kind of overlooked this potential area of visual signaling and visual communication, primarily because it’s not something that our own eyes perceive."

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