Color in Feathers Resists Bacterial Degradation

close up photograph of blue, green, and red bird feathers

Biological Strategy

Parrots

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Protect From Microbes

In living systems, microbes play important roles, such as breaking down organic matter and maintaining personal and system health. But they also pose threats. Bacteria can be pathogens that cause diseases. Some bacteria create colonies called biofilms that can coat surfaces, reducing their effectiveness–for example, inhibiting a leaf’s ability to photosynthesize. Living systems must have strategies for protecting from microbes that cause disease or become so numerous that they create an imbalance in the system. At the same time, living systems must continue living in harmony with other microbes. Some living systems kill microbes. Others repel without killing to reduce the chances that microbes will adapt to the lethal strategy and become resistant to it. For example, some pea seedlings exude a chemical that inhibits biofilm buildup.

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Manage Mechanical Wear

A living system is subject to mechanical wear when two parts rub against each other or when the living system comes in contact with abrasive components in its environment, such as sand or coral. Some abrasive components are a constant force, such as finger joints moving, while others occur infrequently, such as a sand storm moving across a desert. Living systems protect from mechanical wear using strategies appropriate to the level and frequency of the source, such as having abrasion-resistant surfaces, replaceable parts, or lubricants. For example, human joints like shoulders and knees move against each other all day, every day. To protect from mechanical wear, a lubricant reduces friction between the cartilage and the joint.

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Birds

Class Aves (“bird”): Eagles, hawks, sparrows, parrots

Birds are evolutionary engineering marvels. They are descended from dinosaurs, but are far from our idea of heavy, scaly reptiles. Of the specific adaptions that set them apart, most notable is flight—although some mammals can fly, birds take the prize for abundance in the skies. Many birds have hollow, lightweight skeletons and specially-designed wings to help them stay aloft. They also have feathers made of keratin that help them stay warm, attract mates, and improve navigation and aerodynamics in flight. In contrast to their dinosaur ancestors, they lack true teeth and have replaced them with specialized beaks and bills.

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Feathers of parrots resist bacterial degradation due to pigments synthesized internally.

Introduction

Parrots are among the most colorful birds in the world, boasting a vivid array of greens, blues, reds, and yellows. These vibrant colors are not only stunning but also play a crucial role in their social interactions and mating displays. Native to humid tropical environments, such as rainforests in South America, Africa, and Asia, parrots face unique challenges in maintaining their plumage. The constant humidity in these regions creates an ideal environment for bacteria and fungi, which can damage their feathers and put their overall health at risk.

The Strategy

Unlike many other birds, which acquire their red and yellow appearance from s in the foods they eat, parrots create their own color-producing compounds. The resilience of parrot feathers against bacterial attacks is largely attributed to these “psittacofulvins” (from the Greek word for parrot, and a Latin term for “reddish yellow”).

Research involving exposure of various colored parrot feathers to the feather-degrading bacteria, Bacillus licheniformis, revealed that feathers imbued with psittacofulvins—especially those that are red—showed a slower degradation rate compared to white feathers, which lack pigments. This protective feature is similar to the function of melanin, another pigment which is known to enhance the resistance of feathers to bacterial damage.

So, how do they do it? Psittacofulvins seem to bind tightly to the β-keratin molecules in feathers, creating a robust pleated sheet structure that hinders enzymes produced by bacteria from accessing and breaking down the keratin. Some feathers still combine structural color with these protective pigments, and research has shown that their protective properties are still just as effective. For instance green feathers, which combine structural blue coloration and yellow psittacofulvins, resist degradation just as effectively as those with only red or black pigments.

The Potential

The dual role of psittacofulvins in parrot feathers—as color providers and as protectors against microbial damage—offers intriguing insights for biomimetic applications. Materials science can draw inspiration from this natural strategy to develop new synthetic fibers and coatings that mimic the protective properties of psittacofulvins. Such materials could then be inherently colored and resistant to microbial degradation, ideal for use in humid or microbe-rich environments.

Additionally, parrot feathers could inspire innovations in sustainable dyeing techniques that integrate microbial resistance into the dye molecules themselves. This approach could reduce the need for additional finishing processes that often involve toxic chemicals, thereby promoting a more eco-friendly textile industry.

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Last Updated January 29, 2025

References

Journal article

Colourful parrot feathers resist bacterial degradation

Biology Letters | 07/10/2010 | E. H. Burtt, M. R. Schroeder, L. A. Smith, J. E. Sroka, K. J. McGraw

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