November 27, 2024, 10:03 am | Read time: 3 minutes
From bright red to brilliant blue, the bright colors of birds and especially the iridescent feathers of parrots are true wonders of nature. But how do they come about, and why do they differ so much from the coat colors of mammals? New studies show surprising similarities and differences that could prove evolutionary connections.
Birds exhibit a vast array of feather colors. However, the reasons behind this diversity have been a mystery for quite some time. By contrast, the hair colors of humans and the coat colors of dogs and cats have been well documented. The pigments pheomelanin and eumelanin, for instance, are well understood. Yet, the reasons for the prevalence of such a broad spectrum of colorful feathers in birds, ranging from red to yellow, blue, or green, have not been as thoroughly investigated. It appears that birds have evolved different methods from mammals to produce these hues. For instance, finches must actively consume foods rich in carotenoids to impart color to their wings and beaks. However, parrots have also developed a unique pigment that produces similar colors. Two nearly simultaneous studies have delved into how these processes function and why both strategies seem to have evolved in tandem.
The unique mechanism behind parrots’ colorful feathers
Although the colors of various birds may look alike, researchers have long recognized that the pigments found in parrots are distinct. This uniqueness is attributed to a pigment known as psittacofulvin, which renders their feathers exceptionally vibrant.
Conversely, in other bird species, the development of feather pigments is primarily influenced by their diet. For example, flamingos consume crustaceans, which gradually intensify their pink hue over time. Songbirds, for instance, favor berries and colorful seeds that aid in the production of carotenoids, enhancing the vibrancy of their plumage and beaks.
Yet, the distinctive pigment in parrots functions differently, as it essentially substitutes for carotene. In the scarlet macaw, for instance, this pigment is responsible for its brilliantly red feathers. Psittacofulvin, however, is also capable of yielding a yellow feather color. The precise manner in which these two distinctive colors transform and become integrated into parrot feathers remained a mystery for an extended period.
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Utilizing DNA testing, scientists have, for the first time, unraveled the workings of this mechanism. In parrots, an enzyme associated with the ALDH3A2 gene facilitates the conversion of a red hue into a vibrant yellow. However, the study on finches revealed a startling discovery for ornithologists. Finches produce their yellow feather color using the same enzyme as parrots! This occurs despite the underlying processes being fundamentally different. It seems that the enzyme responsible for this in birds has remained unchanged throughout evolution—or may have even emerged multiple times. 1
“The simplicity of the underlying molecular mechanism, in which a single enzyme influences the balance between red and yellow pigments, provides an explanation for the extraordinary evolutionary constancy of parrot coloration,” write the researchers who studied parrots. 2 The finch researchers describe it similarly. Their study illustrates how evolutionary transitions between yellow and red coloration could be achieved through “changes in a few interacting genes.” 3
Although research on feather colors and their origins in the avian world is still in the early stages, scientists can already assert that these colors are not merely bright. A study also released in 2024 has documented that these colorful feathers possess numerous other intriguing properties. “They offer protection against photo-oxidation, damaging radicals, and bacterial degradation.” 4 Researchers appear to be at the threshold of comprehending color formation and its implications in birds, with the promise of more groundbreaking discoveries on the horizon.