Without a doubt, feathers captivate our attention more than other bird qualities. But what is its nature, where does the red feather of birds come from? Is it a function of the light that illumes the birds, the nature of the feathers, or a genetic factor popularly called the red factor?
The red gene factor seems to be the most sung explanation, where red factor canaries are described by researchers as the outcomes of hybridization experiments conducted 100 years ago between domesticated yellow canaries and wild red siskins.
However, for the yellow-shafted northern flicker, the “you are what you eat maxim” has proven to be astonishingly true. The eastern North American woodpecker gets its name from a thin tone of yellow that runs through the middle of its dark feathers. In the past few decades, ornithologists, have observed that some bird’s yellow plumage have inexplicably turned red. Initially, the scientists thought that the birds were interbreeding with the red-shafted northern flicker, which resides in the West, but these rare red birds are thousands of miles away.
The answer was traced to their diets: the birds were ingesting red berries according to studies from The Auk. It turns out that red, yellow, and orange tones prevalent in bird feathers derive from the pigments in the food they eat.
The cedar waxwing, with no close red-feathered relative were discovered by scientists to have a steep obsession for berries. So much so that they died of over-binging after eating lots of overripe berries.
In a more physiological argument, every bird color is produced by the interplay of two coloring mechanisms – one structural, the other, chemical. Structural color comes from the scattering of reflected light, while chemical color depends on a range of pigments. The complex arrangement of feather layers enables structure and chemistry (pigmentation), blending to produce the colors that we see.
Why cardinals are red
Pigments can absorb some wavelengths of light while reflecting others. The absorbed color vanishes while the reflected tone becomes what we see. Pigments in the plumage of the cardinal reflect red light and absorb all the other wavelengths. The most common pigments and melanin and carotenoids.
Melanin is responsible for black, brown, and gray colors in birds and mammals. Blackbirds like ravens and crows have melanin in both cortex and the core.
Carotenoid pigments, characterized by red, yellow, and orange feather tones can accumulate through diets such as flowers, roots, fruits, and seeds, and can be modified in different ways.
The dogwood tree develops bright red berries during autumn. It’s a Northern Cardinal’s favorite and a source or red carotenoids. When the cardinal eats these berries, the carotenoid pigments are isolated by the liver and are sent to the blood for deposition in growing feather follicles. These carotenoids are dumped in the cortex only and not in the feather core. The cardinal also obtains red and orange pigments from several seed sources, constantly maintaining its eye-popping red plumage. A caged cardinal that is fed seeds with zero carotenoids will lose its rosy brilliance after repeated molts.