Blue Jays: Are Blue Jays Blue?

blue jay visits backyard
For some reasons blue jays decided to visit my backyard last week. I’ve been more careful about filling my bird feeder. If I get outside with my camera at the same time that the birds visit, I get some nice photos.

blue jay in flight
I was rather excited to see blue jays visiting my tree. Here is a little about blue jays from Cornell Lab of Ornithography:

This common, large songbird is familiar to many people, with its perky crest; blue, white, and black plumage; and noisy calls. Blue Jays are known for their intelligence and complex social systems with tight family bonds. Their fondness for acorns is credited with helping spread oak trees after the last glacial period.

Seems like the blue color is a physics trick: “The pigment in Blue Jay feathers is melanin, which is brown. The blue color is caused by scattering light through modified cells on the surface of the feather barbs.”

More on the blue color on the Wisconsin Natural Resources Magazine:

It’s the same science that explains why the sky is blue.

Feather colors are determined either by pigments, called pigmented colors, or by light refraction called structural colors. Feathers contain two types of pigments. The melanins are sharply outlined, microscopic particles we see as black, dull yellow, red and brown. The lipochrome pigments are diffused in fat droplets and produce brighter yellows, reds and oranges.

When light strikes a pigment, it absorbs all the other wavelengths of the color spectrum except the color we see, which is reflected back to our eyes. Black is produced when all color wavelengths are absorbed and no color is reflected.

Structural colors, produced by selective light reflection, are mostly the blues, greens and violets. Shimmering iridescent colors are produced when light bounces off the grooves and ridges on feathers. The distance between these surface irregularities influences which colors we see. These structural colors change with the angle of view. Most blue structural colors are produced when particles smaller than a light beam scatter light. These blues do not change hue when viewed from different angles.

John Tyndall, a British physicist of the late 1800s, first described how minute particles, usually less than 0.6 microns, absorb the longer red wavelengths of light but reflect or scatter the shorter blue wavelengths. This phenomenon became known as “Tyndall scattering” and accounts for the sky’s blue color that is sometimes called “Tyndall blue.”

In bluejays, the color-producing units are found in feather barbs. These barbs consist of three layers. A colorless, transparent horny outer layer covers box cells, which cover a dark layer of melanin-containing cells. The box cells contain irregularly shaped air-filled cavities that scatter light. When sunlight strikes a bluejay feather, the beam passes through the barb’s transparent outer layer to the air-filled cavities that scatter the blue light and absorb the longer red wavelengths. Any transmitted light that remains after passing through the box cells is completely absorbed by the melanin. The blue we perceive is actually enhanced in intensity by the underlying melanin-rich black layer.

Do you get blue jays where you live? Did you (like me) always think of blue jays as blue?


More bird posts on this blog:

For more Nature Notes:
Nature Notes

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