Colorful feathers of birds are breath-taking. Even a drab feather is an amazing structure. But trying to figure out plumage color is not an easy task as the colors are either formed by pigments or light refraction of the feather macro-and-micro-structures or combinations of both. Heck, sometimes, what we perceive is even due to air pockets in the plumage!
Some pigments (melanin) form as granules while the feather develops from a follicle. Other pigments (carotenoids) have to be eaten by a bird from plant material or preyed upon by an animal that ate the plants. Depending on the reference, melanin and carotenoids are the main widespread plumage pigments. One source states that melanin produces one third of all color of the 10,000 species of birds.
A third group of pigments, porphyrins, produce reddish/brownish tones, like in owls, and sometimes green colors. Unlike the first two groups, porphyrins glow under UV light or appear brighter in birds with ultraviolet (UV) vision. And a porphyrin subset, called turacin, imparts red and green in a limited few species. Another group, the psittacins, (similar to the word “citizens”) only occur in every parrot species.
If that’s not enough to confuse you, some birds use iron oxide from mud to stain their feathers while others may use their preen oil during breeding season as a feather make-up enhancer.
Just know feather coloration is not an exact science!
ONE IN A MELANIN
But let’s concentrate on melanin, one of the main pigments in living cells. Not only do birds have it in their plumage but also in their bare skin and bills. It’s divided into two forms: eumelanin which makes black, gray, and dark brown colors and pheomelanin varies from reddish brown to some yellows to pale buff colors. The amount of each varies in each species. By the way, you know of melanin in your skin but you probably didn’t realize your hair color is also due to melanin.
During feather formation, melanin deposits as small grains that include Copper, Zinc, and Calcium. (Had you ever thought of metals in feathers occurring naturally?). So yes, this pigment darkens the color BUT it also makes the surface stronger and more resistant to abrasion. Some studies indicate this pigment may also help prevent bacteria degrading the feathers.
BLACK FLIGHT FEATHERS
Have you ever noticed white birds with black wing feathers or tips? Those black feathers experience the most stress during flight so the melanins help reduce wear and tear. Also the longest wing feathers, or primaries, extend out farthest from the body and are necessary for precise controlled flight. Here are a few examples:
So my next question is why don’t all flying birds have black primaries? Theorists suggest they don’t fly as fast, they don’t dive through the air, or their primaries are covered by other feathers at rest and therefore protected.
MORE MELANIN FUNCTIONS
Another benefit to black feathers is the increase in heat to them versus the white feathers. One study found up to 9 degrees temperature difference in the black to white feathers. That difference increased air flow and may have made flying more efficient.
Several avian species sport mainly black plumage. Let’s look at feather structure first. The strong shaft (rachis) running down along the middle of the feather has fiber branches along the side called barbs. The rachis and the barbs form the feather vane. Each barb consists of a core and outer cortex with tiny barbules branching off of it. If only the cortex contains melanin, the feather is brown or gray. So vultures or birds with black plumage, for example, have melanin in both the core and cortex. The concentration of it controls the intensity.
What’s interesting to me is how the Black Vulture primaries look brown, gray, or silver depending on light refraction. If the melanin concentration controls intensity, shouldn’t those wing tips be black? I’d be curious about a study to determine the amount of metals in those wing tips versus the body plumage. On the other hand, er uh, wing, perhaps all the other black plumage compensates somehow in heat and metal distribution. Just something I wonder about.
Meanwhile enjoy a variety of images that are primarily black and white with different locations on these examples. By now you realize the origin of the black color in feathers originates from melanin while white feathers usually lack melanin and carotenoids. (Some studies indicate white feathers contain melanin too.)
Stay tuned for more colorful pigments of missed information in Parts 2 and 3!
CELEBRATE NATURE IN EVERY COLOR
REFERENCED SPECIES LIST
Wild Turkey, Meleagris gallopavo, Guajolote Norteño (Spanish)
Sandhill Crane, Antigone canadensis, Grus Canadiense (Spanish)
American Flamingo, Phoenicopterus ruber, Flamenco Americano (Spanish), Mekoh (Mayan)
Great Kiskadee, Pitangus sulphuratus, Luis Bienteveo (Spanish), X tacky (Mayan)
American White Pelican, Pelecanus erythrorhynchos, Pelícano Blanco Americano (Spanish), Sak p’onto’ (Mayan)
White Ibis, Eudocimus albus, Ibis Blanco (Spanish), Koko (Mayan)
Wood Stork, Mycteria americana, Cigüeña Americana o Galletán (Spanish)
Black Vulture, Coragyps atratus, Zopilote Común (Spanish), Boox pool ch’oom (Mayan)
Anhinga, Anhinga anhinga, Anhinga Americana (Spanish), Chowak kaal (Mayan)
Black-and-white Warbler, Mniotilta aria, Chipe Trepador (Spanish), Tun tun che’, Boox yeetel sac (Mayan)
Black-necked Stilt, Himantopus mexicanus, Monjita Americana (Spanish), Ook Che’e (Mayan)
Bare-faced Curassow, Crax fasciolata, Pavón Muitú (Spanish)
White-winged Dove, Zenaida asiatica, Paloma Alas Blancas (Spanish), Saak pakal (Mayan)
Black-bellied Whistling Duck, Dendrocygna autumnalis, Pijije Alas Blancas (Spanish), Pijiiji (Mayan)
DISCLAIMER: References do not agree about this information.
Sal a Pajarear Yucatán, Bird & Reserves of the Yucatan Peninsula, A Guide to the Birds of Mexico and North Central America,The Handbook of Bird Biology, A Dictionary of Birds, The Sibley Guide to Birds
Cherie Pittillo, “nature inspired,” photographer and author, explores nature everywhere she goes. She’s identified 56 bird species in her Merida, Yucatan backyard view. Her monthly column features anecdotes about birding in Merida, Yucatan and also wildlife beyond the Yucatan.
Contact: email@example.com All rights reserved, ©Cherie Pittillo