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Melanized Barbules Helped Plum-headed Parakeet Feathers Appear Green

Male plum-headed parakeet feeding on a branch in Jim Corbett National Park
Research · Anatomy & morphology

A study of plum-headed parakeet (Psittacula cyanocephala) feathers found that their green appearance depends on an interaction between light-scattering nanostructures and melanin in different parts of the feather. The researchers used a colour change in which plucked green feathers regrow yellow to separate the optical roles of feather structure and pigment. The barbs form the main branches of the feather vane, while barbules are the finer branches extending from them.

Yellow feathers kept the nanostructure that can produce green

They compared how green and yellow feathers reflected light and examined their microscopic and nanoscale structure with electron microscopy and structural analysis. Yellow feathers still retained the spongy keratin–air nanostructure inside the barbs that is capable of producing structural green. The loss of green appearance therefore could not be explained by disappearance of that nanostructure alone.

Melanin in the barbules changed how the whole feather looked

Instead, reduced melanin deposition increased feather brightness, especially at longer wavelengths, and reduced the purity of the green colour. The researchers found that feathers were perceived as green when structurally green barbs occurred together with melanized barbules. When the barbules lacked melanin, the overall reflectance shifted toward yellow.

The results show that the visible plumage colour is produced by several feather components acting together: nanoscale structure in the barbs provides structural colour, while melanin in the surrounding feather microstructure changes how that colour is expressed in the complete feather.

Sources and image credit

  1. Debruyn, G., Dobson, J. L., D’Alba Altamirano, L., Wybouw, N., Nicolaï, M. P. J., & Shawkey, M. D. (2026). Disrupted Melanization Reveals a Hidden Role of Microstructures in Green Plumage Coloration. Integrative and Comparative Biology, 66, icag135. https://doi.org/10.1093/icb/icag135Primary peer-reviewed article first published 25 July 2026. The study used spectrophotometry and electron microscopy to separate the contributions of melanin, feather nanostructure and microstructure to green coloration in plum-headed parakeet feathers.

Image: Male plum-headed parakeet (Psittacula cyanocephala) feeding in Jim Corbett National Park, India, 22 March 2023. Photo: © Giles Laurent, gileslaurent.com / Wikimedia Commons. CC BY-SA 4.0. Representative species image showing the green plumage discussed in the study; the bird was not part of the research. · CC BY-SA 4.0 · Source

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