Brilliant ‘SuperRed’ Feathers Are Created By More Than Just Pigments

Feather microstructures can remarkably change the appearance of red plumage without any corresponding changes in either pigment concentration or molecule types

by GrrlScientist for Forbes | Twitter | Newsletter

NOTE: This piece was a Forbes Editor’s pick.

Adult male Brazilian tanager (Ramphocelus bresilius) is a member of a sexually dimorphic genus of tanagers that have enlarged shiny whitish or bluish-grey lower mandibles, which are pointed upwards in courtship. (Credit: Dario Sanches / CC BY-SA 2.0)

Many birds have brilliant plumage colors, but why? There are several non-exclusive hypotheses may explain the reason(s) that birds invest so much energy into obtaining colorful pigments and creating ornamental plumages:

1. coloration may help species identify each other, so they can avoid producing hybrids, which are often sterile, thereby preventing a waste of time and energy (ref).
2. beautiful ornaments may reflect arbitrary aesthetic preferences in the choosing sex (usually the female) (ref), and may either be maintained through a runaway evolutionary process (ref), or may occur as a side effect of selection on another trait such as foraging, which is known as “sensory bias” (ref)
3. color may indicate individual quality (“honest signaling hypothesis”) through physiological linkage, resource trade-offs, or direct/indirect costs (ref, ref, ref & ref)

Of these three hypotheses, the honest signaling hypothesis has received the most…