Where Does Feather Color Come From?

Birds are highly colorful—perhaps one of the highlights of nature. Whether in the vivid reds of the Northern Cardinal or the iridescent blues of Blue Jays, these colors are more than just flashy accessories; they have critical functions related to communication, camouflage, and mate choice. But what creates all this color?

This article reviews the natural bases of feather color and considers the interplay between pigments, structure, and light reflection that work together to produce their fantastic range.

Why Do Feathers Have Color? 

Where does feather color come from, how is such a diversity of colors produced, and what are the evolutionary consequences? Avian pigmentation has different molecular bases, from simple melanins to more complex carotenoids and porphyrins. Additionally, the microstructure of feathers can influence light and change their coloring to iridescent or non-pigment-based.

·   Feather Colors:

Feather colors range from the vivid reds and oranges of a Scarlet Macaw to shiny blacks and iridescent blues in the Common Grackle. These colors are produced by both pigment deposition and the complex feather structure at a microscopic level.

·   Bird Pigmentation:

Most bird pigments stem from two pigments: melanins and carotenoids. Black, brown, and gray are produced by melanins, whereas reds, yellows, ochres, and oranges in everything living that is not a plant or bacterium result from carotenoids.

·   Feather Structure:

The structure of bird feathers also plays a significant role in their color. The microstructure of a feather can also confuse us about color because we are looking at the way light interacts with it rather than its pigment content to determine what colors will be reflected. This interference and other qualities unique to keratins allow for bright iridescent structural coloration arising through different refraction-wavelength interactions inside and outside the protein fibers.

·   Melanin in Birds:

Melanin is the most frequently found pigment in birds and also provides color hues of brown or black. So, the North American crow sports iridescent black feathers due to high melanin content. Likewise, the speckled pattern of a Barn Owl is caused by how melanin is distributed across its feathers.

·   Carotenoids in Birds:

Carotenoids are pigments birds obtain from their diet, producing bright reds, oranges, and yellows. The vibrant red of the male Northern Cardinal and the orange breast of the American Robin are both due to carotenoid pigments.

·   Iridescence in Birds:

Iridescence is the effect where feathers change color depending on the angle at which they are viewed. Examples include males of species such as the Peacock, which has beautiful iridescent blue and green tail feathers.

·   Structural Coloration in Birds:

Structurally, structural color is an optical phenomenon that produces color due to light-reflecting structures rather than pigments. For example, the Blue Jay is not technically blue; its color results from light scattering through the feather structure.

·    Blue Pigment in Birds:

Interestingly, actual blue pigment is lacking in birds. In birds such as the Mountain Bluebird or Hyacinth Macaw, blue coloration is structural (rather than pigment)—light rays are scattered in a way that produces uniquely bright and unmistakable blues.

 

The Chemistry and Physics of Feather Colors

The principles of chemistry and physics are at play in feather colors by combining pigments embedded in feathers and the light scattering on structures of feathers.

In birds such as the European starling, the sheen is produced by interference in structures, referring to micro-layers within structures in the barbules of the feather. Like most birds, the colors of parrots, including the Blue-and-Yellow Macaw, are due to a combination of pigments and the arrangements of the feathers.

The Role of Pigments in Bird Feathers

Pigments are the most common source of color seen in many bird species. These pigments are either synthesized by the bird or obtained through its diet.

·   Melanins:

Melanins contribute to the black color and variant shades seen in birds. One example is the Great Cormorant and its consummately black plumage, achieved through an overabundance of melanin deposition. Melanin provides color and strengthens feathers, making them hard to break.

·   Carotenoids:

Carotenoids are naturally occurring compounds that a bird gets from its diet and produce vibrant colors. The deep hues of some specimens, such as the American Goldfinch and the pink plumage of the Flamingo, are iconic representations of carotenoid pigmentation. Birds use these colors to signal their health and quality, often influencing mate choice.

How Birds Obtain Pigments Through Diet

Birds obtain pigments through their diet, and because of this, they are sometimes called chromophoric birds. Birds do not synthesize carotenoids, which must be ingested from the food they feed on.

In flamenco birds, for instance, the pink feathers are produced from carotenoids obtained from the algae and crustaceans that these birds eat. In the same way, the vivid red of the Scarlet Ibis stems from the diet containing carotenoids, therefore making it true that birds feeding on carotenoids can develop red plumage.

Melanin, on the other hand, is produced from amino acids by birds, and hence. At the same time, the environment influences melanin production. It does not strictly depend on the diet of carotenoids. The House Sparrow, whose color is brown and black, illustrates melanin produced within the Bird and not the external diet.

Structural Coloration in Bird Feathers

Structural color is a type of bird coloration that results from the microscopic structures within the feathers rather than pigments. 
The colors of this gorgeous bird, this butterfly and this sparkling Opal, they don't come from pigments. These colors come up from the amazing nanoscopic topography of their structures, not the compounds they contain. It's called structural color. We've been borrowing, copying and mixing pigments for tens of thousands of years.

Just look around you, almost everything we make has some kind of dye or paint in it. If we could make our own structural color, it would be next level. White light from the sun contains every color, and color is determined by wavelength. The colors in these paints come from pigments. Molecules that absorb some wavelengths of light and reflect others based on their molecular structures.

So if something looks red, that means it absorbs all the wavelengths of light that we can see except red. Mostly, pigments have a double bonds or complex ring structures that absorb light energy. But over time as more and more light bombards pigment molecules, that energy breaks down their chemical bonds. This decreases the amount of light that the pigment surface can absorb, causing it to reflect a wider range of wavelengths and appear closer to white.
In other words, the pigment fades. But pigments aren't the whole color story, some of the brightest, most stunning colors in nature work differently. They come from nano structures, like the ones on these wing's scales. When light waves hit the morpho butterflies scales, these tiny ridges bounce the light in a way that adds together the amplitudes of only a certain color.

The amplitude or height of a light wave is what determines how bright it is. When the crests align like this, that color pops, a phenomenon called constructive interference. Structural colors work because of how tiny the formations are, often only a few hundred nanometers across. How much do you have to zoom in to see these structures? - So this is way smaller than let's say the thickness of your hair.
Imagine having to see like a fraction of that under the microscope. - If you know what to look for, structural color is all over the place in nature. Many organisms have it and they all evolved their own unique style.
Another example is the brightly colored, iridescent structures of the Male Ruby-throated Hummingbird’s throat, it has multiple layers of structural color that cause it's feathers to shimmer. The microscopic platelets within the feather reflect light in different directions.

For example, the blue color of the Eastern Bluebird is blue not because of the existence of blue phthalo mercenaries but because of the dispersion of light within the cavities that a particular feather consists of. It is due to this that is referred to as the Tyndall effect that causes the brightly colored bristles in many bird species.
A  group of researchers decided to try leapfrogging evolution. They wanted to see if they could put any color on anything they wanted, and they started with this one. This mountain bluebird is serving looks, I mean look at those feathers. That blue, it's gorgeous, I wanna wear it, I want it as a nail Polish.
This blue bird gets its stylish hue from an incredibly complicated pores keratin structure, with lots of holes like a sponge. 

Light Reflection and Refraction in Bird Feathers

Light reflection and refraction are crucial to creating structural colors in bird feathers. As has been noted, when light strikes a feather, some light is reflected off the feather while some goes through the feather, with some bending at various degrees.

For example, in Anna’s Hummingbird, light reflected off the feather gives the outer surface of the feather the characteristic iridescent appearance. The outer structure of the feather is designed with layers of Keratin and air between them, and when it is exposed to light, it gives a twinkling effect.

Peafowls, particularly the Indian peafowl, also show this phenomenon; the distinct coloration derives from the multiple-layer reflection of light to conform to the desired dyeing color.

Conclusion

Mostly, the colors in bird feathers come from chemical pigments, creating spectacular colors and patterns with the help of physical structures. Be it the pigments they must obtain from their food supply, as in the case of the Northern Cardinal obtaining carotenoids, or the structural coloring, as in the Blue Jay, these colors are essential in the lives of birds. They determine how and whether an organism behaves to adapt to a particular environment or multiply; therefore, the study of feathers’ coloration is a matter of beauty and importance. Knowing the origin of feather color helps us know more about the evolution process and birds' social and ecological relations.