Last updated January 24, 2018 at 2:31 pm
Birds of paradise are amongst nature’s greatest animals. During mating they choreograph incredibly intricate dances to attract their mate – usually involving displays of their plumage to show off complex designs and bright colours.
Now, scientists have found a special advantage some species have for making their plumage seem extra colourful and vibrant – their black feathers have unusual structures that make them so black they rival anything humans have ever created.
In many species of bird, males have deep, black, velvety plumage patches immediately adjacent to brightly coloured patches. These black plumage patches have a strikingly matte appearance and appear profoundly darker than the normal black plumage of closely related species. The effect of these incredibly dark patches is to create more contrast, making the colours seem brighter.
The secret to these extremely black areas has been found to be complex microstructures that help the feathers absorb up to 99.95% of light.
Left: normal black feather from Lycocorax pyrrhopterus; Right: super black feather from the Parotia wahnesi
Using techniques to study the microscopic fine detail of the feathers, including spectroscopy and scanning electron microscopy, the researchers found the ultra-black feathers have a complex arrangement of microscopic filaments covering them. These filaments are arranged vertically but tilted, with the effect that they significantly increase the scattering and absorption of light and result in approximately 1% of the reflectance of normal black feathers.
This is not dissimilar to the structure of the blackest substance made by humans, VantaBlack. Using an arrangement of vertical carbon nanotubules, when light strikes the Vantablack surface it bounces between nanotubes until it is absorbed. (However Vantablack has nature beaten, absorbing 99.965% of light)
This super black feather of Ptiloris paradiseus, the Paradise Riflebird, still appears ultra black even when coated with gold.
The light scattering effect of the feathers is best viewed from particular angles which line up with looking down and into the long deep cavities between the tips of the microfilaments. This helps explain why, in nature, bird displays are often performed while keeping the audience at a particular angle to the feathers, increasing the effect of the super-black feathers.
The nett effect is that the super-black feathers reduce light reflectance back to the viewer, which tricks the audience’s mind into thinking there is less ambient light in the area that they’re looking. This alters the viewer’s ability to estimate the correct brightness of a coloured feather patch next to it, making it appear almost self-luminous or to float in space.
And with those brighter colours making a more dazzling and impressive display, the bird with the super-black feathers is more likely to end up with a mate.
The research has been published in Nature Communications
Main image courtesy of Ed Scholes
Feather images courtesy of Dakota McCoy
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