Green-headed Tanager (Tangara seledon): Remarkably Colorful
Daniel Field
The vibrantly hued songbird, referred to as Tanagers, captivates observers with a concealed layer of black or white beneath its vivid plumage.
Artists frequently layer white paint on canvas to amplify the colors applied atop, enhancing their vibrancy. Surprisingly, this appears to be a technique utilized by birds long before humans wielded brushes.
Rosalyn Price-Waldman from Princeton University and her team uncovered this phenomenon in a Tanager species, Tangara, which boasts striking red or yellow feathers, typically concealed beneath a layer of white. Conversely, those adorned with blue feathers possess a black underlayer.
To delve deeper, they extracted 72 feathers from mounted Tanagers at the Natural History Museum in the Los Angeles County Collection.
The researchers photographed the feathers against various backgrounds, measuring changes in light reflection or absorption, ultimately revealing that the underlying layer enhanced the color of the top layer.
Red and yellow hues are produced by pigments that selectively absorb light, which enhances the brightness of backscattered light from the white layer underneath, according to Price-Waldman.
In contrast, blue feathers derive their color from nanostructures within the feathers, which scatter light rather than absorb it. Thus, the black underlayer intensifies the blue hues. “Without a white layer beneath, blue feathers appear grey,” explains Price-Waldman.
The intricate effects of feather coloration arise from their layered structure, resembling tiled roofs. When assessing a single feather, one might find a vibrant tip, a middle section that is either black or white, and a fluffy base. When these feathers are layered on a bird’s body, the tips create adjacent layers of color over either white or black underneath.
Blue Feathers in the Crown of a Red-necked Tanager (Tangara cyanocephala): Enhanced by an Underlying Layer of Black Feathers
Rosalyn Price-Waldman, Allison Schultz
Price-Waldman and her team also discovered that these feather layers can create noticeable color variations between males and females.
“We’ve found instances where females have black beneath yellow and males have white beneath yellow,” she reports. “When placed against the same backdrop, they appear quite alike until the male and female feathers are displayed against a black background, revealing a marked difference in color.”
This color-enhancing strategy has been observed in numerous other songbirds, including manakins and cotingas.
“Substantial research has been conducted to understand how birds produce such stunning colors, yet much remains to be explored,” explains Chris Cooney from the University of Sheffield, UK. “It seems that this ‘hidden’ method for intensifying feather color may indeed be widespread across various bird species.”
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Source: www.newscientist.com
