Tree swallows' iridescent feathers change from blue-green to
muted yellow when exposed to humidity. The plumage reverses to
previous color tones as humidity decreases. This discovery by
Chad Eliason, a University of Akron integrated bioscience Ph.D.
program student, and Dr. Matthew Shawkey, assistant professor of
biology and integrated bioscience, is published in the Sept. 27
issue of Optics Express, the international journal of optics.
The finding has implications ranging from technology (color and
vapor sensors) to biology (mate choice), according to the
researchers. Color in iridescent feathers is created by light
scattered from nanoscale structural components (keratin and
melanin) of the plumage. The researchers explain separate
research that shows that the protein, keratin, absorbs water
vapor, which leads to swelling over a range of humidity.
Further, the nanoscale arrangement of keratin and melanin at the
outer edge of iridescent feather barbules results in coherent
scattering of light, thereby produci