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I recently found an article talking about the colors of bird feathers. https://www.smithsonianmag.com/science-nature/why-are-some-feathers-blue-100492890/ Apparently, unlike other colors, where pigmentation is at fault, blue feathers are actually blue thanks to their unique structure. According to the article, when the feathers grow, they form air pockets, which then form a pattern that just so happens to cancel out the red and yellow wavelenghts, leaving us with blue.

Now, of course, all feathers have the ability to trap air. It's what makes them such excellent insulators, as air conducts heat very poorly. Bonus points if the air is contained in very small cells, as that increases a materials insulation qualities. It's for the very same reason we also use foam for this. Now my question is: As the blue feathers contain miniature air pockets to give them their color, would that make them, in essence, better heat insulators than the ones of other colors, or do all feathers have such pockets, and the blue birds just so happen to be arranged differently, without actually changing any insulation capabilities?

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  • $\begingroup$ This article nature.com/articles/s41467-018-05898-8 is likely relevant to an answer, though it deals with the impacts of reflectance on thermal loads, rather than insulation. In short, other attributes of feathers have large effects on their thermal properties, and can be evolved independently of visible colour. Any direct impact of colouration on insulation might be lost in the noise from these other factors. $\endgroup$
    – bshane
    Feb 21 '20 at 0:10
  • $\begingroup$ As an aside (and from memory), a colleague of mine looking at the costs of sexual ornamentation in blue wrens (Malurus cyaneus) was convinced that blue feathers are worse insulators, based on behavioural observations of males that had molted into blue feathers and others that had not. There was an experimental intervention using testosterone implants, which would cause a male to molt into blue if it wasn't in blue already. I can't find a paper detailing the findings though, so she might not have published them. $\endgroup$
    – bshane
    Feb 21 '20 at 0:18

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