We have bluebirds and blue jays. We have blue and hyacinth macaws, and even blue parakeets. Some swallows are blue, and visitors to the Pacific Northwest of the United States can find Steller Jays. And all of these birds have this one thing in common:
They’re not blue.
And now you’re saying “Of course, they are.” And I agree that they “look” blue, but what you’re seeing is a trick of light.
Blue is a rare color in nature, and historians debate over whether ancient western civilizations even knew what blue was. When we see blue birds or butterflies such as the striking blue morpho, they stand out because it’s an unusual thing to see. And standing out is what you want if you’re a bird, usually a male, trying to attract a mate.
Many animals get their pigment from what they eat. Flamingoes, for example, are pink because of the algae they consume. The algae contains chemicals called carotenoids, which yes, give carrots their orange color. Oh, and if you’ve heard that flamingoes get their color from shrimp, that’s only somewhat true. The shrimp get their color from the algae, the primary source of the pigment.
If flamingoes stop eating carotenoids, their feathers turn grayish-white. So, what if they ate something blue like blueberries? Blueberries are colored with anthocyanins, which differ from carotenoids in that they are broken down by the bird’s digestive system. Flamingoes who eat blueberries will stay grayish-white.
Birds you see that are blue accomplish this feat without the use of pigments at all. As the feathers or scales form, they create a pattern that cancels out red and yellow light and reflects back blue. This is called a structural color, because there’s no actual blue pigment involved. If you crush a blue feather into dust and look at it, it will probably be brown or yellow. Try that with a pink flamingo feather, and it will stay pink. Also, if you shine light through a feather or butterfly wing, the blue will disappear. The prismatic effect only works with reflected light, not light that passes through. Click for a longer, higher resolution video of the blue morpho wing.
And of course, now that that’s all explained, a bird comes along to ruin everything. One bird manages the seemingly impossible and creates its own blue pigment*. The great blue turaco is well-named as it has bright blue feathers. The pigment is made of copper and comes directly from their food, though it can take up to a year to accumulate enough to start coloring feathers. Different turacos have unique red and green pigments as well, making this a special genus of birds. And some mandarin fish have blue pigment too, but in general, if you’re seeing a blue animal, it’s only blue because light is being filtered through a structure. And though there are birds with green pigments, many of the green birds you see are employing this prismatic effect.
So, the next time you see a blue jay or even a common pigeon, take a closer look at the colors you’re seeing that aren’t really there.
*I’ve since learned that turacos create only green pigment, and they’re the only bird to do so. Once again, the blue is a prismatic effect, though this time it’s based on green feathers.