I think I have been whacked up the back of the head by the “gauntlet” :o)
This entry is attributed to Beth’s entry yesterday over at Nutwood Junction, and my subsequent comments (and her diligent investigation at www.straightdope.com/columns/000728.html). So, I humbly present to you, Blue – Not What You Think.
Oddly, there is absolutely NO pigment to make feathers blue. So how can we possibly have such vivid blue birds as Indigo Buntings, Blue Jays, and bluebirds? Their feathers don't produce that color with any chemical. Instead, the color is produced simply by the way some cells are arranged on the feather. This makes blue a STRUCTURAL color. Blue jay feathers contain particles so small that they cause selective scattering (reflection in all directions) of the shorter wavelengths of light, which collectively appear blue. In the jay, the cells containing these microscopic particles are underlain by another cell layer containing the dark pigment melanin. The contrast of blue against a dark background makes the color stand out.
Blue and green pigments are virtually unknown in birds, having been found only in an African species known as the turaco. In other birds, including your jays, bluebirds, etc., the blue is merely a trick of the light, producing what ornithologists call a structural color or schemochrome. Grind up a blue feather--no blue. For that matter, hold a blue feather up to the light, so that you're seeing it by transmitted rather than reflected light, and you'll find the blue disappears.
In parrots you've got the same basic structure, except that the blue-producing layer is overlain by a transparent yellow layer. Blue masked by yellow produces green. White feathers are also schemochromic. They look that way because they reflect all colors, but they contain no pigment and under certain conditions can be shown to be transparent.
Seeing is Believing
If you can find a Blue Jay feather, see how bright it is when light shines on it. Then hold it up to a light source so light passes through it, and see how it turns brownish gray when you see the true pigment color!
8 comments:
Good summary! [putting my gauntlet away]
I found several other sites that answered the same question, and in the same way. So I think this solves the Mystery of the Blue Feathers.
Beth
Breaking news from Nutwood!
I have a blue jay feather framed and on a shelf above the TV. We had to satisfy our curiosity, so I took the feather out of the frame. We held it under the light and looked at it: blue. When we held it up to the light, with the feather between us and the light: tan. No lie!
We had to try it outside, too, so we walked out on the deck, and when we held the feather up to the sun: tan.
Amazing! Try it for yourselves if you get a chance!
Beth
I never knew that!
Missie
(Ducking Beth's gautlet) Jeepers she takes the facts to heart doesn't she (winks)...I'll have to try that experiment with the Blue Jay feather (by the way I was doubtful myself). (Hugs)Indigo
I think that makes perfect sense. I am always trying to make
a correlation between science and religion, and it stands to reason
that the Creator had used so much blue to paint the oceans and
the skies that he ran a little short when it came to the birds and
the flowers, hence, so few blue ones! LOL. Just a thought!
That is fascinating information but.....I just love to enjoy Blue Jays etc. because they are beautiful, no matter how they got that way...LOL. Your head is so full of detailed information, I hope you also just enjoy stuff. And I know you do so I am obviously just giving you a hard time. grin
Hugs, Joyce
... do you ever listen to Ira Flatow on 'Science Fridays' on NPR's 'Talk of the Nation' ..? Your blog goes one better ..! I really learn thing from you entries ..!
very interesting! thanks!
natalie
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