Megan Hobratschk
Have you ever wondered why some birds are so colorful compared to others? The color of a bird’s feathers is determined by structural elements and/or pigmentation, which are colored substances. In one special case, discussed later, feather color is produced by a combination of both.
When thinking of colors in general, pigmentation is what comes to my mind. In terms of feather color, there are three types of pigmentation. The first type of pigment is melanin, which is the same pigment that produces different hair colors and skin tones in humans. The concentration of melanin, or lack thereof, found in a feather results in white, brown, or black feathers, and can also produce feathers that are reddish-brown and pale yellow. Interestingly, many birds have darker feathers on their wings, as feathers with higher amounts of melanin are stronger and more resistant to wear.
The second type of pigmentation is carotenoids, which is the same pigment that results in the orange color of a carrot! Like in a carrot, carotenoids produce oranges, yellows, and red in a birds’ feathers. Lastly, the most diverse feather pigments are known as porphyrins. Porphyrins fluoresce under ultraviolet light and can result in pink, red, brown, and green feathers.
Another source of color in feathers is structural. Structural feather color is produced as light refracts, or bends, off of keratin proteins in the feather. This is the same protein that makes up our hair and nails! Structural feathers can be iridescent, like in hummingbirds, or non-iridescent, like in Blue Jays.
You may have realized that the color blue was not mentioned when discussing pigmentation. Interestingly, blue is one of the only feather colors that is almost exclusively produced structurally. If you find a blue feather from a Blue Jay on the ground, try backlighting it by holding it up to a light. Because the blue light is no longer being reflected back, the feather will appear brown from the melanin present in the feather.
I want to specifically highlight the color green in bird feathers. There is only one group of birds in the world that has true green feathers: the Turacos. Turacos have a special copper pigment known as Turacoverdin, which produces their bright green coloration. You might think, “I see birds with green feathers all of the time!” While this is true, most green color in birds is produced by a combination of yellow pigment and blue structural color. This means the green feathers on most birds aren’t actually green, they just appear that way due to the mixing of yellow pigment found in the feather and the scattering of blue light by the small structural elements in the feather.
As the weather cools down, I encourage you to take a few minutes from your day to see how many different colored birds you can find in your area. You might be surprised by what you find!
Photo Caption: A Green Turaco
Photo Credit: Ian Wilson, CC BY 2.0, <https://creativecommons.org/licenses/by/2.0/>, via Wikimedia
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