Painting the Bunting: Carotenoids and structural elements combine to produce the feather coloration of the male Painted Bunting.

This article investigates the mechanisms behind the diverse feather coloration of the male Painted Bunting (Passerina ciris), focusing on six distinct plumage patches. Using methods including digital photography, spectrophotometry, carotenoid extraction, and high-performance liquid chromatography, the study demonstrates that all feather colors result from a combination of metabolically derived carotenoid pigments and feather nanostructures producing structural color. Notably, it identifies for the first time that purple rump feathers arise from the combination of red ketolated carotenoids and blue structural coloration. The findings reveal that carotenoid concentration, melanin presence, and nanostructural tuning vary independently across patches, contributing to the bird’s complex coloration and providing a foundation for future research on the physiological and evolutionary roles of combined pigmentary and structural colors in birds.