You know that Crows are black, so why am I writing about the color of Crows?
This is why…
Look how colorful this adult crow is — showing off its pale iridescent brown and blue feathers. What happened to the glossy black color of this crow?
This photo image is not due to the way the light happened to hit the Crow on this spring morning. It is instead what happens to Crow feathers after most of a year of use. The melanin pigment that makes the feathers dark brown to black has faded to a rusty brown color, and the structural elements covering the melanin granules in the feather that made them look shiny or glossy have broken down. Now, tiny air gaps in the feathers simply reflect short wavelengths of light, which we see as blue. And the combination produces the blue-brown look of this crow’s plumage.
Crows molt once a year at the end of the breeding season. As the new feathers gradually lengthen and replace the old ones, high concentrations of melanin pigment are deposited in the shafts and barbs of the feathers making them look black, and a layer of keratin laid down on top of the melanin granules in the barbs will make the feather look glossy.
A crow hunting on the grass in the backyard last fall was a much darker color after molting new feathers.
Just as I was about to leave the one of the parks on the Mississippi River that I visited today, I heard bluebirds singing in a nearby tree, so I tried to track them down. They never let me get close, but the contrast of the males’ bright blue feathers against the rusty brown of old oak leaves was striking enough to make some nice photos.
The bright blue really makes this bird stand out, but the rusty brown breast feathers just matched the color of the oak leaves.
Some males seem to be much bluer than others, and the females (upper left) have paler rusty breast feathers and much less blue in their wing and tail feathers.
My long-term blog readers may recall from earlier posts that the blue color is structural, rather than the result of a pigment. Tiny air spaces in the feathers contain particles (like dust) that scatter and reflect short wavelengths of light so that the feathers appear blue to our eyes. In the wrong light (i.e., indirect), the bright blue feathers just look slate gray.
A poorly lit subject without direct sunlight on his blue back looks a little less blue.
Bluebirds are not very cold tolerant birds, and we may still experience more spring snowstorms and sub-freezing temperatures, so I hope these guys haven’t arrived too early.