Colorful Feathers

 Even the plainest bird brings fascination to a quiet view.

Warbling Vireo

Most birds go far beyond plain‒they are adorned in patterns important to their own purposes and exciting to us humans with our monochromatic skin tones, which we embellish with clothing and ornaments.

Rose-breasted Grosbeak

Birds achieve these arrays mostly through pigmentation, a process as familiar to us as putting paint on a canvas except that in their case it is through the grace of genes. 

Cape May Warbler

Pigments are variable substances independent of the structure of the feather. Depending on their molecular structure they absorb particular wavelengths of light. The wavelengths they reflect back to us give us sensations of specific colors.

The most common group of pigments are melanins that produce colors ranging from darkest black to reddish browns and pale yellows. The melanins we and many other animals incorporate determine the color of our hair and skin.

Brant

Melanin provides more than just coloration. Feathers that contain melanin are stronger and more resistant to wear than feathers without melanin. Feathers without any pigmentation are the weakest of all.

Northern Gannet

Many otherwise all white birds have black feathers on their wings or black wingtips. These flight feathers are the ones most subject to wear and tear. The melanin causing the tips to appear black also provides extra strength. *

Scarlet Tanager, male

Most reds and yellows come from a class of pigments called carotenoids. These are produced by plants, and are acquired by eating plants or by eating something that has eaten a plant. Carotenoids are responsible for the bright yellows seen in goldfinches and as well as the brilliant hues of the male Scarlet Tanager.

Scarlet Tanager, female

Carotenoids can interact with melanins to produce colors like the olive-green of the female Scarlet Tanager.

American Wigeon

Spectacular effects can also be produced in some birds by iridescence, a structural quality of the feather rather than a pigmentation.

Tree Swallow

Iridescence is the result of refraction of incident light from the microscopic structures of feather barbules. The coloration of Tree Swallows is not only beautiful but glowing when seen from the right angle.

Mallard

Refraction works like a prism, splitting the light into rich component colors. As the viewing perspective changes, the refracted light gives a shimmering display beyond hues.

European Starling

Iridescent feathers change color with different viewing angles. The effect is caused by exceedingly thin layers of protein in the structure of the feather barbules. From an aesthetic standpoint they give redemption to glittering individuals in the invasive hordes of European Starlings.

Indigo Bunting

Not all structural colors are iridescent. Tiny air pockets in the barbs of feathers can scatter incoming light, resulting in a specific, non-iridescent color. Blue colors in feathers are almost always produced in this manner. Examples include the blue feathers of bluebirds, Indigo Buntings, and Blue Jays. 

If you find one of their feathers you can see for yourself how this works. First, observe it in normal lighting conditions and you will see the expected blue color. Next, try back-lighting the feather. When light is transmitted through the feather it will look brown. The blues are lost because the light is no longer being reflected back and the brown shows up because of the melanin in the feathers.

Bay-breasted Warbler

Melanins have been harnessed into wonderful patterns like the Bay-breasted Warbler. Besides these and the carotenoids there is a third pigment group the porphyrins that are produced by modifying amino acids, mostly in the otherworldly plumage of tropical birds.

The feather structures of many species also reflect light in the ultraviolet range. Because many birds can discriminate a greater variety of colors than humans, including ultraviolet wavelengths, they can appear quite different to each other than they do to us. Presumably that is how crows can tell each other apart. 

Least Sandpiper

Certainly rainbow-hued plumage gratifies my eye. Then too, I'm thankful for even the most modestly colored birds. 

* Much of the technical information in this posting comes from an article "How Birds Make Colorful Feathers" on the website of the Cornell Lab Bird Academy, 2015.