Structural Color in Birds - Blue Feathers Are Not Blue!

Every blue feather you've ever seen has a secret - there is no blue pigment in ANY bird in the world. No kidding! Please subscribe to continue learning what makes life AWESOME: biobush.tv/subscribe
Almost every green feather is the same, and so is every white feather. Why does nobody tell us these things!?
Today you're invited to view this secret world and learn how it works with nano-scale structures that reflect light. I got some beautiful footage of different feathers.
Also, in a first for this channel, I recorded good audio in the field!
BIRD SENSES
Vision - BioBush.tv/birdvision
Smell - BioBush.tv/birdsmell
Hearing - BioBush.tv/birdhearing
Taste - BioBush.tv/birdtaste
Touch - BioBush.tv/birdtouch
Bonus Senses - BioBush.tv/birdnavigation
Ask Two Zookeepers - BioBush.tv/a2z
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New animal videos every Friday. Life is AWESOME. Learn why!
I'm tweeting about birds at - / biobush
And now Instagram at - / biobush
Thanks for watching! You're awesome!
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Learn about some awesome birds in "Birds of Prey - Full Wildlife Documentary 2019"
• Birds of Prey - Full W...
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[@batmanshadow8888]

The theory behind is photonics crystal

[@BioBush]

AHHH THANK YOU! Thank you Batman Shadow! I have been stuck at that level of understanding for so long, and you just opened the gates to new levels. How did you learn about photonic crystals?

[@batmanshadow8888]

@@BioBush Hi, I am sorry that I didn't use KZbin for the past two years. I am a research fellow in a university. My research topic is nanophotonics and metamaterials. My favorite research is structural colors or we called plasmonic colors. I published some articles about physical colors on the journals like Laser Photonics Reviews and Applied Physics Reviews

[@BioBush]

Batman Shadow! You have become a legendary story I tell people. I did not have the concepts to look up structural color, and then Batman Shadow came out of nowhere, told me what I needed to know, and disappeared. :) It's now one of my favorite topics to teach about, because it's all around us and so few people already know about it. Can you link me to any of your work, or email it to me? (email is on my profile) I would always like to learn more. Also, if you ever want to come on the channel to talk about structural (plasmonic) color, you are welcome here!

[@batmanshadow8888]

@@BioBush the title of the article is ‘Colors with plasmonic nanostructures: A full-spectrum review’ published on Applied Physics Reviews

[@1Kraxmaskin]

Thank you for the interesting video. However, according to my litterature on the subject, Turacoes are NOT the only birds with green pigment (turacoverdin). Also birds from Ithaginis and Rollulus families, and some Jacanas produce turacoverdin. Another kind of green pigment are produced in feathers of Somateria and Nettapus birds.

[@BioBush]

That is so interesting, Kraxmaskin! It's always risky to say that "all" or "no" animals have a trait, because there are so many exceptions. I am impressed by your knowledge and admire your ability to share it. I will start saying that fact correctly! Thanks for watching!

[@tedberber1451]

This is why at the edge of the parrot feathers, it is a light blue not a dark blue because at the edge there are more bubbles which form shorter distances.

[@BioBush]

That is SO cool! You have some rare knowledge, Ted. Only about 1/100 of people I talk to have ever heard of this. Thank you for sharing your knowledge with the rest of us!

[@Umeko236]

Thanks! I was super intrigued about the green feathers of my parrots, and this made it easy to understand :)

[@BioBush]

That's great, Umeko! Green is so interesting because it's a mix of both methods - structural and pigment. So it can be used to teach about both. And now you have that cool trick where you hold a green feather up to a light and it turns grey. There are so many interesting things to learn about birds. Thanks for watching!

[@Umeko236]

@@BioBush You're right! Thanks for creating this content! :D

[@user-yk4kv1pl3d]

the crazy hidden world is your channel!

[@BioBush]

Thank you for the kind words, Yizue! Take care!

[@williambo5989]

blue was expensive pigment in the past for artists. so Rembrandt used some optical tricks to create the illusion of blue in this paintings. when you see blue in an old painting the patron commissioned it to show status.

[@BioBush]

That is a really cool fact! Thanks for sharing. If you have time, I would like to hear an example or two. Thanks for watching, Wattana Bo!

[@williambo5989]

@@BioBush sure i will find 2 examples

[@williambo5989]

@@BioBush What color is smoke? The simple answer is that it depends on the color of the background you see it against.Smoke against a dark background appears blue.Against a light sky the same smoke will appear orange. Sometimes an observer will see smoke passing upward from a dark forest background to a light sky background, and it will actually appear to to shift from one color to another. These colors are not an intrinsic quality of the smoke in the same way green is intrinsic to green colored glass. The color is a result of the behavior of the light rays as they pass through the smoke. As M. Minnaert explains: "Against a dark background, the smoke is illuminated by rays from the sun falling on it obliquely from all directions except from behind; these rays are scattered by the smoke in every direction and some of the scattered rays enter our eyes and make the smoke visible. The particles which make up the smoke scatter blue light much more than red or yellow: therefore we see the smoke as blue. On the other hand, when the background is bright we see the smoke by transmitted light and it appears yellow because the blue in the incident white light has been scattered in all directions, very little can reach our eyes, and only the yellow and red remain to be transmitted and give color to smoke." When the particle size of smoke increases (such as when each particle is encased in a tiny droplet of water) it loses these scattering properties, and the smoke appears relatively white. Smoke can also take on specific colors if certain chemicals are introduced into it (think colored smoke bombs).

[@williambo5989]

@@BioBush kzbin.info/www/bejne/apKTd5WHma1mmrs

[@williambo5989]

@@BioBush kzbin.info/www/bejne/hIHFm4J4jtefjqM

[@moose_sauce2938]

Very cool, I now know why my roosters tail feathers are bluish purplish and greenish depending on the angle, thanks so much !

[@BioBush]

Yes! They use the thin-film method. If you're looking straight through the reflecting layer (minimum thickness) it looks one color, and if you look at an angle (maximum thickness) it looks the other color. Isn't it interesting how these properties are all around us and almost nobody knows about them?

[@marcopohl3236]

As far as I know, blue pigments tend to have toxic metabolic byproducts, which is why no non-toxic animals have them (it's just easier to make structural colors than to get rid of the waste) I don't know why poisonous\venomous animals don't have it though Edit: kzbin.info/www/bejne/b5THoIN6apaVpMk

[@BioBush]

Oh, that was cool. Thank you for sending that link over! You were right about the toxic metal byproducts. And they tend to be unstable. I learned something new today. Thanks, Marco!

[@marcopohl3236]

@@BioBush But again, I have no idea why toxic animals don't use them, sounds like a free toxin to me

[@aliescritora4892]

I'm learning a lot from your videos ♥ THANK YOU SO MUCH!

[@BioBush]

You're welcome Hart and Hart! There are so many interesting topics in bird shapes and behaviors. Thanks for taking the time to learn about them!

[@aliescritora4892]

@@BioBush will visit your channel more often!

[@DrMSSR_tips_tricks]

Ur viedoes r awesome....the way of explaining is good

[@BioBush]

Thank you, Public Channel! There are so many interesting things to learn about birds. Thank you for watching!

[@erikm9768]

Great video! Is there a solid definition how to differentiate pigment vs structural color that is a little bit more meaningful than just chemical properties vs structural properties? The way I see it, chemical properties also come from properties of the molecule which is similar to structure, but on a slightly different physical scale. Both chemical pigments and structures kind of absorb the light its not reflecting (structures by trapping it which eventually should lead to absorption). Please elaborate if you can, im curious for a scientifically sound explanation for this. Thanks!

[@BioBush]

I love your question, Erik! It shows you are building your own mental models based on processing what you learn, which is an amazing trait. Your question made me process as well. Because you're right, pigment molecules absorb and reflect different wavelengths of light based on their physical properties. The difference must lie in what happens after the light is reflected. In structural color the reflective surfaces are spaced to cause constructive interference for the target color (blue) and destructive interference for other colors. (For a better physical explanation of what's happening see BioBush.tv/blueBYE). So the structural color only works in its macro 3D structure. If you grind up a pigment into a fine powder, even to a powder of single molecules, it will still retain its color. If you grind up a structurally colored material fine enough it will be colorless, or the color of any pigment molecules in it. So for a rigorous definition I would go for either a) causes constructive interference from multiple reflecting surfaces or b) has preferential reflective properties at a macroscopic level but NOT at a molecular level. A complete answer is probably worth a Master's degree. I hope this helps, and please keep the interesting questions coming!

[@BirdWatchwithANUKUSUMAKARKADRI]

Dear Steve Bush, it's surprising to learn there are no blue pigment in birds feathers. Wow Thank you very much for your detailed explanation about it. I liked your video very much😍🙏 Thank you for sharing 🙏 Fantafaboulus Friday dear friend 😍📹🌷🦋🐦

[@BioBush]

This is one of my favorite bird facts, because it's everywhere and almost nobody knows about it. Now you do! Thank you for watching and for your kind words, Anu!

[@melodyivers]

Fascinating!

[@BioBush]

Absolutely, Melody! Structural color is such a good thing to know about, because it is all around us and almost nobody knows about it. But now you do! Thank you for watching!

[@abdulrahmanalfouzan7023]

المقطع مفيد في فتح خيارات متعدده لاختيار اضاءة مناسبه وتنويعها بغرفة انتاج الطيور

[@BioBush]

Glad you found it helpful, Abdul! This is one of the most fun things to learn about birds, that blue is caused by the shape of their feathers. Thanks again for watching!

[@xuxuoficial]

What a lovely explanation

[@BioBush]

Thank you, Juliano! There are so many interesting things to learn about birds. Thanks for watching!

[@KoawNature]

Very cool topic! I put a link to this video on my site's bird feather ID page. Hope you don't mind Steve!

[@BioBush]

Oh, hey! I just got back from watching your toad video. Thanks Koaw! I'm glad you found some value in this video. It's a really fun thing to hold a blue feather up to the light and watch it turn grey. You now have the ability to blow someone's mind in about 30 seconds. Enjoy! Also, thanks so much for linking to the video. :) Keep up your great work in connecting people with nature!

[@KoawNature]

@@BioBush It really is mind blowing! You keep up the great work too!

[@eucolecionodinossauros]

Fascinating video!

[@BioBush]

Thank you Eu coleciono dinossauros! I'm glad you enjoyed it. It's likely that dinosaurs used similar tricks in their skin and feathers, but it wouldn't fossilize well.

[@zeusland8247]

When is a blue bird not blue? The answer to this question is always. There actually is no such thing as a blue bird. To find out why, Smithsonian Insider asked Scott Sillett, a wildlife biologist at the Smithsonian Migratory Bird Center. “Red and yellow feathers get their color from actual pigments, called carotenoids, that are in the foods birds eat,” Sillett explains. “Blue is different―no bird species can make blue from pigments. The color blue that we see on a bird is created by the way light waves interact with the feathers and their arrangement of protein molecules, called keratin. In other words, blue is a structural color. Different keratin structures reflect light in subtly different ways to produce different shades of what our eyes perceive as the color blue. A blue feather under ultraviolet light might look uniformly gray to human eyes.”

[@BioBush]

Zeus Land, thanks for the tip! I've experimented with red lamps (because that's what we have) and couldn't figure out how to demonstrate that if the wavelengths are missing, the blue will vanish. Does ultraviolet light mean a "black light", do you think?

[@HRTsAFyre]

@@BioBush try an ultraviolet avian bird light. Same kind they use when a bird is indoors and cannot get enough sunlight. The feathers dull when they get no UV light. They also see much more colors in the ultra violet light spectrum than we can possibly see.

[@BioBush]

@@HRTsAFyre Thanks for the insight! I like exploring structural color and coming up with different ways to explain it. It's this amazing natural wonder, and it's all around us, and almost nobody knows about it. Same thing with bird vision. And lungs. And bones. There are so many interesting things to learn about birds! Thanks for taking time to learn.

[@HRTsAFyre]

@@BioBush don't birds have air sacs instead of lungs?

[@HRTsAFyre]

@@BioBush when does.the keratin sheath come off of a very large feather? I'm referring to macaws tail feathers or flight feathers. Does the thick sheath just remain at the base as the feather grows out completely? When the blood supply stops will it come off on its own, or is the bird supposed to remove it at that point?

[@floofygod]

Wow. So amazing and intriguing. I had to search for this video because blue pigment did not make sense in my mind. I guess I was right!!

[@BioBush]

You were right! In vertebrates there are only two species of fish that are actually blue. Blue mandrill face is structural, blue feathers, blue scales, even blue eyes in humans. None of it is pigment. It's a fun thing to learn about and it's a fun thing to teach others. Thanks for watching!

[@floofygod]

@@BioBush Thank you to for making such an engaging and clear video!!

[@hershey995]

Beautifully explained 💙👏

[@BioBush]

Thank you, Harsha! It's this interesting feature of birds which is all around us but almost nobody knows. Thank you for taking the time to learn, and I hope you have lots of fun teaching people this fact!

[@Monster33336]

Much like the effects of rayleigh scattering that makes the sky appear blue. Maybe someday we'll have the technology and dyes to see more if our lenses allow us to. I heard DMT and certain drugs can help, not necessarily open your eyes to new colors but more visually convincing and brighter.

[@BioBush]

You're right! Rayleigh scattering is off of small particles. This is Tyndall scattering off of large particles. But in general terms they are both scattering of light based on the physical shape of objects. I am super looking forward to people figuring out reliable structural color. I think every room and object is going to get interesting new properties. The future is full of wonderful things to imagine. Thanks for watching this other video, Calvin!

[@00713926]

Brilliant 👏

[@BioBush]

Thanks again, Afrozen! I'm glad you enjoyed this. Thanks for taking the time to learn about birds!

[@Ecotasia]

It is weird how turacos are the only green pigmented birds.

[@BioBush]

Here's the theory I heard: there's (relatively) lots of copper in the soil where turacos live, so they get lots in their diet of fruit. Turacin is a porphyrin (protein with a metal bit like hemoglobin and iron), but with a copper atom. So they may use copper-intensive pigment because there's so much around? And other birds do it the other way because it works?

[@Ecotasia]

@@BioBush that is a really interesting theory

[@00713926]

Awesome

[@BioBush]

Thanks, Afrozen! There are so many interesting things to learn about birds. Structural color is a good one to know. Thanks for watching!

[@joshuacommons6025]

If there is no blue pigment in mammals where do blue eyes come?

[@BioBush]

Good conclusion, Joshua! It's structural color; blue eyes come from protein structures in the iris. In humans at least it's parallel ridges of protein that cause blue light to bounce out with constructive interference. Dark blue eyes then also have some melanin behind the protein to absorb other colors, making the blue really stand out. So you can see structural color at work in people's eyes. As far as I know these proteins are in every eye, even ones with more melanin that masks their presence. I really like that you drew this conclusion because it shows you were processing, not just watching. Thanks for the great question and thanks for taking the time to learn about birds!

[@christabelle__]

I love that blue birds have been fooling us all this time! But what I want to know is what color birds perceive these 'blue' birds to be - do they also see the color as blue like we do, or to them does it look gray/brown/etc? That's a question I can't seem to find an answer to - I always wondered what purpose being blue served, if it makes them stand out to a predator's eye... but maybe the light refraction is something we see differently than they do?

[@Katheter07]

At. 4:18 you show incident rays being blue and yellow. This doesn't exist. The photons of light have a broad frequency spectrum. Upon encountering the bubbles, the blue frequencies (or wavelengths) scatter coherently, while all other colors do not. When the broadband photons (or "rays") encounter the pigment layer, green and blue wavelengths are absorbed, leaving yellow to reflect.

[@seandmaccormack.8528]

Natures colour nanotechnology.

[@BioBush]

Exactly! And we would be wise to emulate it. Color that doesn't fade in sunlight, uses common materials, produces no toxic byproducts, and can very easily look metallic or change color based on viewing angle. Seems like something we could use! Thank you for watching, Sean!

[@marcopohl3236]

The dude with the dragon design here again: I came up with the idea that Dragons might have different colors in their feathers and scales as a means to tell them apart (individuels, not species) maybe with blue being the base color (so an albino would be blue instead of white) does that make sense?

[@BioBush]

Hi Marco! Sounds fun! I think there's a lot of precedent for different dragons being different colors. But the idea of having individual patterns is genetically feasible (see striped/spotted animals, whose pattern is determined by both genes and development). The deep blue requires a dark base pigment to really show. The idea is that the blue bounces out off the structures and black pigment absorbs everything else before it can also bounce out. If the black pigment isn't there then everything else bounces out too, making white light with slightly stronger blue than anything else. So an albino would be white with a really soft blue tinge. I really like these questions. Nice to hear from you again!

[@marcopohl4875]

@@BioBush I wasn't sure if different dragons with different colors really made sense as usually members of the same species have similar coloration and many of the colors don't have an obvious survival benefit (brick-red isn't good camouflage in most places, after all). does it still check out?

[@BioBush]

@@marcopohl4875 Social birds can have ridiculously bright colors with a survival benefit. Bright colors help keep the flock together, and all of them looking out for predators together is what keeps the individuals safe. So that's one route if they're social. Another bright color thing in nature is aposematism, which is bright warning color that the animal is dangerous. Dragons would possibly qualify, even if their only predators are other dragons. Oh, and then mate selection plays a strong role in many species, so if there's a preference for vivid colors, unique patterns, or both, then they could easily be maintained despite their uselessness in hunting/life. I'm editing pictures of Northern Cardinals. Being red doesn't seem to bother them much. I like how much thought you're putting into this! Even if the story doesn't make you famous you're going to know a lot more about biology. Keep up the good work!

[@marcopohl4875]

@@BioBush Thanks again. About my story: I have a lot of creative projects, some I actively work on, others are just creative exercises to keep my mind sharp, (I'm using different variations of the dragon design based on what fits the setting, for instance) let's hope that one makes it ;P As for dragons: aposematism usually warns about toxins, but I guess fire would lead to similar selection pressures too, especially since (depending on what ignition system I end up using to explain fire breathing, the jury's still out on that) they might have evolved from a venomous ancestor anyway. It would make sense for dealing with predators: dragons are often depicted as rivals to cats, particularly the Panthera genus (the most well-known example would be Asia, where the dragon and the tiger symbolize power struggles, but it happens in other places too) so to explain this, maybe dragons are preyed on by panthers in childhood and develop different personalities based on how they deal with them, which is in turn informed by color: so green dragons, for instance, might be aggressive if they grew up in the tundra, but not in the forest, opposite for white, and reds are always aggressive, which works since red symbolizes aggression anyway. social is a bit tough since dragons are more solitary, but since they are highly intelligent at worst and straight-up sapient at best they might have some social tendencies (they understand the concept of a relationship, they just don't have a lot of them)? is there maybe some in-between of solitary and social, which they could be?

[@BioBush]

@@marcopohl4875 My mind got spinning on the ignition system. A two-stream spit of fuel plus oxidizer? There are auto-igniting mixtures (hypergolic) so you don't need a spark. Anyway, what you asked is about social systems, and I can assure you that 100% of social systems exist in animals, and you will not come up with something that is weirder than what animals are already doing. I have a question about the dragon/panther dynamic, which is: are dragons R-selected or K-selected (lots of babies, little investment, or few babies, much investment)? I'm wondering why the dragons don't organize more of their society around preventing predation of their children. If they're R-selected then whatever, there are 20 more from that clutch and only one will likely survive to adulthood anyway. If they're K-selected then organizing to prevent panther predation (and therefore changing how dragon personality development works) sounds like a good plot for a story.

[@shumhin6413]

interesting

[@BioBush]

Hi Shum! This is such a fun thing to know, because you'll start to see it everywhere. Thanks for taking the time to learn about birds!

[@uppensai2922]

i have been bamboozled my whole life ;-;

[@BioBush]

We all were. Structural color is all around us, but almost nobody knows about it. Now you do! Thanks for taking the time to learn!

[@habeebunissanooman8363]

@@BioBushdefinitely it’s a huge learning Had never heard before anything called as STRUCTURAL COLOUR

[@NashKaimana]

yeah bro

[@mitchebe]

God's creation is amazing!

[@BioBush]

Yes, there is wonder in every place we look. We have a beautiful world to explore and take care of. Thank you for watching!

[@LaraCroft2169]

They see color different,y then we do. The way they make color may affect how they see each other. This would become selective for breeding and survival.

[@ShabazzTBL]

He lost a little cred when he said “birds, animals...” as if birds weren’t animals but ill give him any other shot at it. Edit: He earned it all back and more by proving knowledge in the random facts we all love to collect. Haha

[@BioBush]

Thanks for sticking with the video when I lost cred at the 2 second mark. :) Words are hard sometimes. I did study biology at the university level and have several years' experience as a professional zookeeper, if it helps. Anyway, structural color is the takeaway from this video, which is a bit of knowledge worth acquiring from even an imperfect presenter. Thanks for watching, Shabazz!

[@ShabazzTBL]

@@BioBush haha I was joking. It was an interesting view though. I enjoyed it. I also got my degree in biology so I love this type of stuff.

[@ShabazzTBL]

@@BioBush I actually was going to go with zookeeper also but as I’m sure you know they don’t seem to like to pay zookeepers plus I got more interested in human medicine. I still think it would have been a cool job though.

[@BioBush]

@@ShabazzTBL Accurate on both counts. Nobody gets into zookeeping for the money. Human medicine is much more lucrative, depending on the specific job, and human biology is equally fascinating. I'm glad you found a way to use your degree.

[@ShabazzTBL]

@@BioBush oh...sorry to inform you that I’m actually not. I got a second degree in respiratory therapy and that’s what I’m doing now haha. Eventually I’ll get a third. For a bit I was still going to go the zookeeper route but my local zoo is the Columbus Zoo which is always in the running for number one and so it’s competitive to get a job there and I didn’t get into the internship so I had to find something else. Working in a lab was 100% out of the question haha. And I have to salute you because, while I’m not rich, I make just about twice as much as I would have there( and they pay better than average) and things are still not easy. So I know you’re making a sacrifice to do this. Very noble in my eyes.

[@FrankTheAmazing]

I know your secret...

[@lovelynore8296]

Nonsense

[@BioBush]

Hi Nore! Do you take issue with any particular part of this? There are many surprising things to learn about birds, and structural color is one I'm still wrapping my head around. Anyway, I appreciate you watching!

[@habeebunissanooman8363]

@@BioBushu r so positive 😊

[@mishaa4140]

Hello, I have an important question which I hope you will be able to answer. I watched the ‘blue feathers’ and ‘green feathers’ parts of this video, but I still have a question which I would like you to explain to me. I have two blue colored (and with grey and white feathers) Rosecollis Lovebirds/Agapornis birds. One of them passed away in 2021, he was 6 years old and about 8 months. I had him since he was 6 months old. My other parrot is now 7 years old and about 9 months. I have him too since he was 6 months old. (The question): ❗️A long time ago (but I don’t know when exactly), all of sudden the color of some (a few?) of their blue feathers turned into green!! Especially the ones on their wings (dark blue feathers). Do you have any idea what could’ve caused this? Aging? Was there some kind of pigment or something that showed up after they aged a bit more? But they were younger back then. I found this; beautyofbirds.com/peach-face-lovebird-mutations/ Here they are showing color mutations, but they are not explaining why it happens. 🤦🏻‍♀️ I can’t really find a good answer to my question, especially not in the language ‘Dutch’. English gives better results, but I have still not found a good answer yet. I’m still looking. I emailed a Vet about this. I hope to hear from them soon. I hope it has nothing to do with an illness or anything like that. (Long story short; His wings are often vibrating. My other parrot’s (the one who passed away in 2021) his wings were vibrating like that too, so I hope it’s not an illness. I’m talking to a Vet about it. I already got him more vitamins and minerals and I will also get him jodium and something against parasites (in case it has something to do with those stuff. I’m sure he doesn’t have parasites, but just in case it’s a parasite that’s in “resting mode” and wakes up when his immune system weakens (I hope not). Some people (and Vets) say vibrating wings like that can also be caused by parasites. The Vet wanted to check him and take a blood test, but they say my parrot has to stay for that at the clinic and “it may take some time” AND “it’s very rare, but there is a possibility he might die because of the stress”. OH H3LL NO, I’m not gonna risk that!! Other than this wings vibration, he’s perfectly healthy. I’m not gonna let them stress him like that. And he’s an elderly bird, since he’s 7 years old and 9 months, so he’s probably also more sensitive to stress than younger birds. (Besides, he lives like a King in my house and he’s so spoiled, he never has to really stress about anything! XD )) - Well, I hope you will be able to answer my question about the color change in feathers. Regards, D.

[@mishaa4140]

I meant Roseicollis** Not ‘Rosecollis’.

[@BioBush]

Hi Mishaa! I haven't heard of a bird changing color mid-life, but I can think of two possible mechanisms (though not the underlying causes). The first, as you suggested, is that they have some latent genes that have turned on to start producing yellow pigment. An experiment I have read about but never tried is to expose the feather to UV light, which will eventually break down the yellow pigment but leave the structural blue untouched. Apparently it takes a week or two under a UV light? If you know anyone with a pet reptile they probably have a UV light. I would like to replicate that someday, so let me know if you try it. The second mechanism is that when the structural bubbles change, the reflected wavelength changes. For example, blue parrots tend to turn green-blue when they take a bath because water changes the average size of air bubble (probably by swelling the keratin matrix between bubbles). So what to DO? If you try the UV light experiment and it turns your green feather blue, then you know you have a healthy green bird! Any other result I have no idea what is happening or what is causing it. I hope this was helpful, and let me know any updates!