The many colors of feathers

by Tammy Mercer

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One Saturday morning in June, the Early Birders and I watched for activity in the wetlands. Before long a tiny green bird zipped into view and perched on a branch. We weren’t sure if it was a male or female ruby-throated hummingbird until it turned its head. The throat feathers of the male caught the sun and lit up into the most beautiful bright red color. We all “oooooh’d” as if we were at a spectacular fireworks display. How could a tiny patch of feathers elicit such a response? What gives birds their color and artistry? Photo - Ruby-throated Hummingbird. ©Creative1 Commons

Nature's Canvas - Feathers

Feathers are made of keratin, as are our hair and fingernails. Feathers are made of a strong central shaft, with barbs branching out on opposite sides and barbules branching off the barbs. Birds have many kinds of feathers, but flight feathers and body contour feathers tend to show the most color.

Like our hair and fingernails, feathers are no longer living tissue and cannot be repaired as they experience wear and tear. Birds must molt, shedding their old feathers at least once a year as they grow new ones. Growing new feathers takes a lot of energy, and birds do best with this when food is plentiful. Photo - Male Mallard. ©Tammy Mercer

Nature’s Color Palate

Neutrals: Melanins: Melanin is the substance that makes the blacks, browns and grays of a bird’s plumage. It also colors our own skin and hair. Birds produce melanin, which is deposited directly into the feathers as they grow. Melanin adds strength to the feathers, which is why birds often have darker wing and tail feathers where the strength is needed most. Such totally black birds as crows have very strong feathers. Almost all birds have some melanin in their feathers.

Neutral colors provided by melanin are important camouflage to help birds hide from predators. Females especially need to blend in when they are on the nest. For many birds, the amount of melanin varies as the feather grows, which leaves patterns of lighter and darker colors in the feathers. Owls, hawks, shorebirds, sparrows and many other birds are primarily colored with melanin.

Warm Colors: Carotenoids: Carotenoids make up many of the reds, yellows and oranges found in feathers. Unlike melanin, animals cannot produce carotene. Birds must obtain these pigments from their diet, which is then deposited in growing feathers. A bird that is less skilled at finding food will have less colorful feathers.

Bright colors in a male’s plumage tell other male birds that he is a strong contender and will defend his territory well. Males with less brilliant plumage usually have a harder time defending a territory. Bright feathers also tell a potential mate that this bird eats well and will be a good provider while raising young.

Goldfinches, housefinches, scarlet tanagers, cardinals, orioles and many others owe their beautiful warm colors to the quality of their diet.

below it still absorbs all the other colors. This is the case with the most brilliant blues we see in blue jays, indigo buntings and eastern bluebirds.

Cool Hues: Structural Colors: While carotenoids can, at times, provide some cool colors in some birds, most blues are created by the way light is reflected from the surface structure of the feather itself. The keratin that makes up the feathers sometimes has very tiny pockets of air. The shorter wavelengths of light in the blue end of the spectrum will bounce off these air pockets, making the feather appear blue.

Structural blue does not appear in all light. If you hold a feather up to the light, you will see pigments— carotenoids or melanins—through the feather. You will not, however, see structural blue. If a blue feather is immersed in liquid and the pockets filled, the feather will not reflect blue light until it has dried.

How Nature Mixes Colors:

Now that we have our color palate, we can begin to see how nature mixes colors. Let’s start with the color green. If you were working with paint, you would probably mix yellow and blue together to make green. For olive green, you could start with yellow and add small amounts of black or brown until you obtained the desired color. Nature does something similar. For some birds, both yellow pigments and structural blues combine in the feathers to make green.

Or maybe melanin is deposited in the barbs and yellow carotene in the barbules of a feather to make an olive color, which is very common in warblers and other birds. Usually a blue bird will have melanin deposited in the feather’s barbs and barbules with a layer of clear, bubbled keratin on the surface. In some light the feathers will appear brown or gray. But when the light hits the feathers, the blue light is reflected/refracted by the bubbles in the keratin while the melanin object or feather, combined with light from within the structures. The common grackle has all-black plumage due to melanin deposited in the feathers. But when viewed in sunlight, you can see a gleam of multiple colors, including purple, green and bronze. Iridescent colors change with movement and light and can completely disappear at times. Blue Jays. ©Creative Commons

The ruby throat of the hummingbird is an iridescent color that is sharply focused into red wavelengths. Pigments cannot begin to produce a red color like this. The bird can turn its head and the throat will look completely black. But when it turns into the light the brilliance of the ruby throat is dazzling.

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References:
Ehrlich, Paul R., David S. Dobkin, and Darryl Wheye. 1988. The Birder’s Handbook: a Field Guide to the Natural History of North American Birds Simon & Schuster Inc. NY, NY.

Farrant, Penelope A. 1997. Color in Nature: a visual and Scientific Exploration. Blanford. London, U.K.

Gill, Frank B. 1999. Ornithology. W. H. Freeman and Company. NY, NY.

Simon, Hilda. 1971. The Splendor of Iridescence: Structural Colors in the Animal World. Dodd, Mead & Company. NY.

Other articles related to birds by Tammy Mercer:

A Great Place for Birding – why the Garden is great for birding, including in May after the Spring migration.

EBWG as a Migration Rest Stop – an article addressed to the birds about the benefits of Eloise Butler Wildflower Garden as a migration rest stop.

Early Birders Catch the Wonders – what wonders are seen during the year on the Saturday Morning Birding walks.

Native Plants - for the Birds – about interactions of plants, insects and bird life. Illustrated.

Rewards of Summer Birding – summer birding and distinguishing fledglings from adults.

Warblers - Spring Warblers and the little time there is to see them. (This is a 1.0mb pdf file)

Winter Survival of Warm-blooded Critters – how some of the birds and animals survive the winter in the Garden.

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Note: This article was published in the Fringed Gentian™, Autumen 2010, Vol. 57 #1. Vol. 58, #4.