A Simple Chemical Shift Explains Why Parrots Are So Colorful, Study Suggests

Flamingos get their signature pink hue by eating shrimp, while boobies’ feet turn bright blue because of their fishy diets.

But how do parrots get their vivid red, yellow and green feathers? This query has long perplexed scientists, but, now, they say they’re one step closer to solving the mystery.

A simple chemical tweak governed by a single enzyme determines the color of a parrot’s plumage, researchers report this week in a new paper published in the journal Science. Their findings not only help answer a long-standing question about parrots, but they could also offer broader insights into evolution and color variation throughout the animal kingdom.

“It is a huge step forward in avian color genetics,” says Rosalyn Price-Waldman, an evolutionary biologist finishing her PhD at Princeton University who was not involved with the research, to NPR’s Ari Daniel.

Most birds do not make their own color pigments. Instead, they get them from their diets. Cardinals, for instance, get their bright red feathers from snacking on berries and seeds that contain naturally occurring pigments called carotenoids. (Other colors—such as blue—result from the way nanostructures on feathers scatter light.)

But parrots are unusual. They don’t have to eat colorful foods to have colorful feathers, because their bodies produce pigments known as psittacofulvins.

“Parrots are the only birds that we know of that make bright colors in this way,” says study co-author Joseph Corbo, a scientist at Washington University School of Medicine, to Chemical & Engineering News’ Bethany Halford.

Scientists have long known about psittacofulvins, but they haven’t fully understood how these pigments work. Why are some parrot feathers yellow and others are red? And what role do psittacofulvins play in this variation?

To try to answer this question, researchers turned to two species of colorful parrots: the dusky lory (Pseudeos fuscata) and the rosy-faced lovebird (Agapornis roseicollis). They took a closer look at the chemical composition of psittacofulvins in these birds.

Psittacofulvins are made up of chains of carbon atoms. When scientists honed in on the ends of these chains, they noticed some chemical differences that appear to be correlated with different hues. In red feathers, these chains of carbon atoms ended with an organic compound called aldehyde. In yellow feathers, the chains ended with a different molecule called carboxylic acid.

In some instances, both aldehyde and carboxylic acid molecules are present. This creates a range of hues in the yellow, red and orange family.

Green feathers, meanwhile, result from yellow feathers topped with the blue-producing nanostructures. Black, gray and brown feathers are produced by an entirely different pigment called melanin.

As a result, parrots have many ways of “mixing and matching these different types of pigments to achieve sometimes unusual colors,” Corbo tells ScienceNews’ Erin Garcia de Jesús.

The team also discovered that an enzyme named ALDH3A2 is responsible for these chemical differences. The amount of ALDH3A2 a bird produces is encoded in its genes, they found.

Their findings demonstrate that “nature often uses elegantly simple reactions to achieve significant change,” says Keith Gordon, a chemist at the University of Otago who was not involved with the research, to Science’s Elizabeth Pennisi.

Researchers now have a better understanding of the chemical and genetic underpinnings of parrot feathers. But many questions remain unanswered. For example, why do parrots make psittacofulvins, rather than getting carotenoids from foods like other birds do? And why did they evolve this capability?

“Are these molecules better than carotenoids in some way?” Corbo tells ScienceNews.

Moving forward, scientists might also be able to use their newfound knowledge to learn more about parrot biology and lifestyle. For example, in blue-footed boobies, the more vivid the feet, the healthier the birds are. Females also look at the dullness or vividness of males’ feet when determining their reproductive fitness.

“People are very interested in what the pigment content of a feather can tell us about an organism’s health or stress or other aspects of its biology,” Price-Waldman tells NPR.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.