How the observed color of the Swallow Tanager (Tersina viridis) changes with viewing geometry

DIANA SKIGIN; MARINA INCHAUSSANDAGUE; CHRISTIAN D'AMBROSIO; ANA BARREIRA; PABLO TUBARO

OPTIK

ELSEVIER GMBH

Año: 2019 vol. 182 p. 639 - 646

0030-4026

Non-iridescent coloration in birds? plumage is associated with the quasi-ordered nanostructuresof short-range order present within the feather barbs. Even though this type of color does notchange with the observation direction, a few bird species which exhibit the so called non-iridescent structurally colored feathers, present significant hue variations as the relative anglebetween incidence and detection directions is varied. Among these, the Swallow Tanager constitutes an excellent system to investigate this phenomenon as its hue changes remarkably fromgreens to blues as the angle between the illumination and observation directions increases, andindependently of feather orientation. In this paper we elucidate the origin of the striking colorchange of the Swallow Tanager plumage by computing the reflectance spectra of the feathers?microstructure. We show that the color observed under different illumination-detection conditions can be predicted quite accurately by applying averaging techniques and by considering theair-spheres microstructure of their feathers? barbs as the main responsible for the observed colorchange. This work opens up new possibilities for the design of devices with special color characteristics.