Biochemical stability and ornamentation

What is it about?

Much of birds’ colorful plumage is created by carotenoids–unstable chemicals that quickly degrade with UV and oxygen exposure. Yet carotenoid-based coloration trends last thousands of years, meaning that birds have evolved ways to deal with carotenoids’ propensity to degrade. This paper examines two mechanisms, metabolic modification dietary carotenoids and selective expression of stable carotenoids, that increase the stability of bird ornamentation.

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Why is it important?

We found that birds depending on fast-degrading carotenoids for color, deposit these compounds immediately prior to breeding. When species evolve the ability to metabolically convert fast-degrading carotenoids, they lose dependency on the timing of deposition. We find that metabolic conversion makes carotenoids more colorful and chemically stable, enabling birds to remain colorful over time despite using unstable chemicals for coloration.