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Jay Feather

Scientists have discovered how birds use sophisticated changes to the structure of their feathers to create multi-coloured plumage that doesn’t fade to grey over time.

Researchers from the University of Sheffield used X-ray scattering techniques at the ESRF facility in France to examine the blue and white feathers of the jay and found that the birds demonstrated a surprising level of control and sophistication in producing colours.

The work used feathers selected from the extensive collection at the Natural History Museum (NHM) in London and the findings were published in Nature Scientific Reports.

The team found that instead of using dyes and pigments to colour their feathers, which would fade over time, the birds use well-controlled changes to the nanostructure of their feathers to create the vividly colours, most likely to help them recognize each other.

Jays are able to pattern these different colours along an individual feather barb, the equivalent of having many different colours along a single human hair.

Jays’ feathers are made from a nanostructured spongy keratin material, exactly the same material that human hair and fingernails are made from.

When light hits the feathers the size of the holes in the sponge-like structure determines how the light is scattered and therefore the colour that is reflected, ranging from ultra-violet through to blue and white.

The research team found that the jay is able to demonstrate amazing control over the size of these holes and fix them at particular sizes, determining the colour that we see reflected from the feather.

Larger holes mean a broader wavelength reflectance of light, which makes the colour white while smaller holes result in the colour blue.

If the colours were formed using pigments created from the bird’s diet, the feather colour would fade over time but as the colours are created through structural changes, any nanostructure will remain intact, which explains why birds don’t go grey as they age.

Humans, however, rely on pigments to colour hair and as there are not produced to the same extent as we age, we go grey.

Dr. Andrew Parnell, from the University of Sheffield's Department of Physics and Astronomy said, "Conventional thought was that to control light using materials in this way we would need ultra precise and controlled structures with many different processing stages, but if nature can assemble this material 'on the wing', then we should be able to do it synthetically too."

He added, "This discovery means that in the future, we could create long-lasting coloured coatings and materials synthetically. We have discovered it is the way in which it is formed and the control of this evolving nanostructure - by adjusting the size and density of the holes in the spongy like structure - that determines what colour is reflected.

"Current technology cannot make colour with this level of control and precision - we still use dyes and pigments. Now we've learnt how nature accomplishes it, we can start to develop new materials such as clothes or paints using these nanostructuring approaches. It would potentially mean that if we created a red jumper using this method, it would retain its colour and never fade in the wash."

Researcher Dr. Daragh McLoughlin of AkzoNobel Decorative Paints Material Science Research Team added, "At AkzoNobel, the makers of Dulux paint, we aim to encourage and stimulate the innovation of more sustainable products that have eco-premium benefits. This exciting new insight may help us to find new ways of making paints that stay brighter and fresher-looking for longer, while also having a lower carbon footprint."

Dr. Adam Washington from the University of Sheffield added: "The research also answers the longstanding conundrum of why non-iridescent structural greens are rare in nature. This is because to create the colour green, a very complex and narrow wavelength is needed, something that is hard to produce by manipulating this tuneable spongy structures. As a result, nature's way to get round this and create the colour green - an obvious camouflage colour - is to mix the structural blue like that of the jay with a yellow pigment that absorbs some of the blue colour."

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