Iridescence in a Raven Feather

March 15, 2008


Referred by: Rebecca Roush
Summary Author: Rebecca Roush 

The common raven (Corvus corax) has not adapted to urban settings like some of its relatives, though there are locations where ravens can be approached and photographed at a close range. This close-up of a raven’s wing was taken at Yellowstone National Park in September 2007. In that setting, with so many homo sapiens in their midst in a highly controlled manner, ravens have learned that humans can be trained to provide food and entertainment in exchange for having their photograph taken. This raven’s wing colors appear to more resemble petroleum on water than the flat black observed from a distance.

Diffraction of sunlight rather than pigmentation is responsible for the metallic hues of these feathers. The tips of iridescent feathers have barbs that contain minute platelets. The thickness of these platelets, which depends on the amount of air (bubbles) within them, determines the colors that are observed.

Then this ebony bird beguiling my sad fancy into smiling,
By the grave and stern decorum of the countenance it wore,
"Though thy crest be shorn and shaven, thou," I said, "art sure no craven.
Ghastly grim and ancient raven wandering from the nightly shore -
Tell me what thy lordly name is on the Night's Plutonian shore!"
Quoth the raven, "Nevermore."

From "The Raven," by Edgar Allan Poe