Why Birds Don't Go Grey as They Get Old: How They Keep Vibrant Colors

Animal fur goes grey as they get older, just like human hair. But birds remain vibrant throughout their lives. Now, scientists have found how birds maintain their multi-colored plumage over time.

In this latest study, the researchers used X-ray scattering to examine the blue and white feathers of the Blue Jay. In this case, the scientists found that the birds demonstrate a surprising level of control and sophistication in producing colors.

Instead of simply using dyes and pigments that fade over time, the birds use well-controlled changes to the nanostructure to create their vividly colored feathers. This could possibly be used for Jays to recognize one another. In fact, the Jay patterns different colors along individual feather barbs, which is the equivalent of having many different colors along a single human hair.

The feather of a Jay goes from ultra violet to blue to white in color. It's made of a nanostructured spongy keratin material, which is the same kind of material that human hair and fingernails are made out of.

The Jay actually gets its color through structure rather than pigments. The size of the holes in the sponge-like structure of its feathers is fixed at different sizes. This determines the color we see reflected from the feather. For example, larger holes mean a broader wavelength reflectance of light, which creates the color white. A smaller, more compact structure results in the color blue. If the feather colors were created by pigments, we could see this fade over time.

"The research also answers the longstanding conundrum of why non-iridescent structural greens are rare in nature," said Adam Washington, one of the researchers, in a news release. "This is because to create the color green, a very complex and narrow wavelength is needed, something that is hard to produce by manipulating this tunable spongy structures. As a result, nature's way to get around this and create the color green-an obvious camouflage color-is to mix the structural blue like that of a Jay with a yellow pigment that absorbs some of the blue color."

The findings are published in the journal Scientific Reports.

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