Published: February 6, 2018

A male Western Bluebird. (Photo: © Tom Grey)

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The gorgeous blue of the Bluebird is produced by the unusual structure of the bird’s feather which reflects light.(Photo: © Tom Grey)

GELLERMAN: Bluebird, bluebird, through my window. Why are you so blue? That’s the subject of this week’s BirdNote ®. Michael Stein has more.

[Mountain Bluebird song]

STEIN: The cheery song of this Mountain Bluebird is a sure sign of spring. [Mountain Bluebird song]
Because of their glowing blue feathers, the three species of North American bluebirds – Eastern, Western, and Mountain – are among the continent’s most beautiful birds. But why are they blue? Well, a Native American myth has the dull, ugly bluebird bathing in a blue lake to acquire its colors. But the scientific explanation is no less wonderful.

[Mountain Bluebird song]

Unlike many other bird colors, blue is not a pigment. It’s a color produced by the structure of the feathers. Tiny air pockets and melanin pigment crystals in each feather scatter blue light and absorb the other wavelengths. That beautiful blue light leaves the feather to dazzle the eye of the beholder.

[Mountain Bluebird song]

And that color is not lost on a female bluebird. Male Eastern Bluebirds that are brighter blue and reflect more ultraviolet light have greater breeding success than their paler counterparts.
Children often ask why the sky is blue, and we can ask the same question about bluebirds. The answer is the same in both cases: it’s a trick of the light.

[Mountain Bluebird song]

I’m Michael Stein.

Song of the Mountain Bluebird provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. Recorded by D.S. Herr.

BirdNote® Why Are Bluebirds Blue? Was written by Dennis Paulson.

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