Curious readers may be interested in this evolutionary feature in Birds 
of Paradise . I have extracted below some paragraphs from a report in 
PhysicsWorld (UK). I don't have the reference to the original papers.

Nari Mistry

========================= Extracted from PhysicsWorld (UK)=====

Male birds of paradise have exceptionally black feathers and now 
researchers in the US have explained how the feathers manage to reflect 
tiny amounts of light. The team found that some feathers have 
complicated structures that create a scattering effect that results in 
almost zero reflectance of light under certain conditions – giving them 
a “super-black” appearance. The researchers think that this black 
plumage evolved to enhance the perceived brilliance of adjacent colour 
patches during courtship displays.

Birds of paradise are found in New Guinea and parts of eastern 
Australia. They are famous for the elaborate courting displays, plumage 
ornaments and dramatic colouration of the males. In many species, males 
have brightly coloured patches of feathers next to matte black plumage 
that appears much darker than the black colouration of other birds.When 
researchers from Harvard University, the Smithsonian Institution, and 
Yale University shone light on museum specimens of five species of the 
bird of paradise they discovered that these black feathers have an 
extremely low directional reflectance – at normal incidence they only 
reflect back 0.05–0.31% of light. In contrast, black feathers from two 
other species of bird, used for comparison, had a directional 
reflectance of 3.2–4.7%. . . . .

(Experiments). . . done by the team revealed that this is a result of 
the feathers' microscopic structure. A typical feather has a central 
shaft with rows of barbs branching off. Rows of smaller barbules then 
spread out from the barbs. In most feathers this structure is flat, with 
everything laying in the same horizontal plane. But the super-black 
feathers have barbules that are covered in microscale (tiny) spikes and 
they curve away (up) from the horizontal plane.The researchers explain 
that these vertically-tilted barbule arrays create deep, curved cavities 
that cause multiple scattering of light, resulting in more structural 
absorption of light than normal black feathers.". . . . These 
super-black feathers even retained their black appearance when coated 
with gold dust, whereas the normal black feathers appeared gold”.

The modified barbules are only present on the exposed overlapping tips 
of the feathers, while those towards the base of the feathers have a 
typical feather structure. Also, the black feathers from the back of one 
bird of paradise species, the superb bird-of-paradise,/Lophorina 
superba/, which are not used during display, had a typical barbule 
morphology and were more reflective than the super-black feathers. This 
supports the idea that the modified feathers have evolved for display 
purposes, the researchers say.

*Nari B. Mistry*,
Ithaca, NY
To see my paintings, visit


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