Why some birds of paradise have ultrablack feathers

Tilt in spiky microstructures generates the birds’ exceedingly dark coloring

Ptiloris paradiseus

BIRDS OF A FEATHER  The bird of paradise species Ptiloris paradiseus sports velvety, ultradark feathers next to its bright blue-green plumage. Microstructures in the black feathers, which help increase how much light is absorbed, are responsible for the extremely dark color.

B.G. Thomson/Science Source

Some birds of paradise really know how to work their angles. Tilted, microscopic filaments in some of the showy birds’ black feathers make that plumage look much darker than traditional black feathers, researchers report online January 9 in Nature Communications.

Dakota McCoy, an evolutionary biologist at Harvard University, and colleagues measured how much light each type of black feather absorbs. Superblack feathers absorb up to 99.95 percent of light that shines directly on them, while traditional black feathers absorb up to 96.8 percent, the researchers found.

Using scanning electron microscopy and nano-CT scanning, the team observed that ultrablack feathers have ragged, spike-studded barbules that curve upward at a roughly 30-degree angle to the tip, creating an array of deep, curved cavities. Traditional black feathers are smoother and lack such detailed microstructures. These spikes and pits scatter light multiple times, allowing for more light absorption and darker plumage, the scientists say. Even when the researchers dusted the feathers with gold, the darkest ones still retained their blackness, while traditional black plumes looked gilded in SEM images.

Superblack patches probably evolved to “exaggerate the perceived brilliance of adjacent color patches” during mating displays, the researchers write.

Ashley Yeager is the associate news editor at Science News. She has worked at The Scientist, the Simons Foundation, Duke University and the W.M. Keck Observatory, and was the web producer for Science News from 2013 to 2015. She has a bachelor’s degree in journalism from the University of Tennessee, Knoxville, and a master’s degree in science writing from MIT.

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