The super black plumage seen in some species of birds of paradise is produced by the arrangement of microstructures in the feathers according to a study in Nature Communications this week. The microstructures help the feathers absorb up to 99.95% of directly incident light.
In multiple species of birds of paradise, 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.
Using a number of techniques including spectrophotometry and scanning electron microscopy, Dakota McCoy and colleagues investigated the role that structural absorption of light may play in black feathers from seven species of birds of paradise (five species had profoundly back plumage and two species had normal black plumage). The authors found that the super black feathers have highly modified barbules - microscopic filaments on feathers - arranged in vertically tilted arrays, which significantly increase the scattering of light and thus can result in approximately only one hundredth of the reflectance of normal black feathers.
The authors suggest that structurally absorbing super black patches evolved because they exaggerate the perceived brilliance of the adjacent colour patches, catching the attention of potential mates during courtship displays.