Birds-of-paradise are renowned for their extraordinary mating rituals, yet their vibrant and rhythmic performances encompass more than what is immediately apparent to human observers.
In a groundbreaking discovery, scientists have observed these remarkable birds radiating stunning beauty in a dimly lit environment.
Researchers from the American Museum of Natural History (AMNH) meticulously examined existing archives and determined that all 37 primary species of birds-of-paradise found in Australia, New Guinea, and Indonesia exhibit biofluorescence. Only a small number of peripheral relatives do not emit a glow when exposed to ambient ultraviolet or blue light.
Most male birds tested possess brightly fluorescent heads, napes, bills, and plumes that glimmer with green or greenish-yellow hues. Some even have fluorescent legs, feet, tails, and rings around their eyes.
Many of these mysteriously colorful patches are starkly bordered by dark feathers with no fluorescence, and these parts of the body are often used in mating displays, when males flap, flutter, sway, bop, hang, and pose in an elaborate, attention-seeking dance that varies from species to species.
Many male birds examined exhibit vividly fluorescent features on their heads, napes, bills, and plumage, which radiate with shades of green or greenish-yellow. Additionally, some species display fluorescence in their legs, feet, tails, and the rings surrounding their eyes.
These strikingly colorful areas are often sharply contrasted by dark feathers that lack fluorescence. Such non-fluorescent regions are frequently utilized in courtship displays, where males engage in a complex array of movements, including flapping, fluttering, swaying, bobbing, hanging, and posing, all of which differ among species.
Other males from different species may use the bright fluorescent patches on the crown of their head as their ‘feature’ piece, contrasted by a black ‘skirt’ of feathers spread out below.
Because females sit on a branch above the male to watch his performance, this fluorescent head would pop from the darkness.
That’s an interesting hypothesis, but it only explains one-half of the picture.
Thirty-six, possibly 37, species of female bird-of-paradise were also found to fluoresce, albeit less brightly than the males, and their glowing parts were typically limited to the patterned and mottled feathers on their chest and belly.
Sometimes, the rings around female eyes also glowed, possibly used as a signal to other birds that they are watching.
More research is needed but it’s possible females are using this biofluorescence for “simultaneous camouflage and communication”, argues the team at AMNH.