Blue Jay feather with light shining from above
Blue Jay feather with light shining from underneath. Notice how all of the blue has disappeared.
Young Naturalists: The Nature of Feathers By Val Cunningham
Have you seen a bright red male cardinal or a blue jay in your neighborhood? The colors you see on these birds form in two different ways: by pigments and by structures.
Pigment colors. Most feather colors are produced by pigments called carotenoids or melanins. Both kinds of pigment absorb certain wavelengths of light and reflect the rest. We see the reflected light as color.
Carotenoids reflect bright yellow, red, and orange light. Cardinals get carotenoids from seeds they eat.
Most birds get their color from melanin, the same chemical that colors our skin. Birds make melanin from chemical building blocks within their bodies. Melanins produce black, gray, or brown colors. Melanin also strengthens feathers. As a result, black wingtips are stronger than white ones are.
Structural colors. The other kind of feather color is not a pigment color. It is what we see when light hits the parts of the feather (structure). We see feather color because light reflects from or scatters through thin layers of cell walls in the barbs.
When the structure of a feather reflects all of the light, we see white. White is a structural color. Blue and most green colors are also structural. Blue jays look blue, but their feathers have no blue pigment. A blue jay’s feathers have melanin below the surface under a layer of bubblelike cells. These bubbles reflect and scatter blue light waves, and melanin absorbs the other colors of light. That’s why the blue jay’s feathers look blue in sunlight. But in the shade, the melanin shows up better, and the feathers look blue-gray.
Iridescent colors, such as a male hummingbird’s brilliant throat patch, also are structural. Iridescent feathers have several layers of bubbles. In some birds these layers are twisted, absorbing or reflecting various wavelengths of light. The layers reflect light as a soap bubble does, with colors shifting as your point of view changes.
Invisible colors. Many birds have patches of feathers that reflect ultraviolet light. Birds can see ultraviolet light, which humans can’t see. So what we see as a black or blue bird might look much more colorful to other birds. A female bird might choose a mate based on the brightness of his ultraviolet feathers.