title: Spectral tuning of Amazon parrot feather coloration by psittacofulvin pigments and spongy structures.
abstract: The feathers of Amazon parrots are brightly coloured. They contain a unique class of pigments, the psittacofulvins, deposited in both barbs and barbules, causing yellow or red coloured feathers. In specific feather areas, spongy nanostructured barb cells exist, reflecting either in the blue or blue-green wavelength range. The blue-green spongy structures are partly enveloped by a blue-absorbing, yellow-colouring pigment acting as a spectral filter, thus yielding a green coloured barb. Applying reflection and transmission spectroscopy, we characterized the Amazons' pigments and spongy structures, and investigated how they contribute to the feather coloration. The reflectance spectra of Amazon feathers are presumably tuned to the sensitivity spectra of the visual photoreceptors.
authors.affiliation: Computational Physics, Zernike Institute for Advanced Materials, University of Groningen, NL-9747 AG Groningen, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: Tinbergen
authors.forename: Bodo D
authors.initials: BD
authors.lastname: Wilts
authors.forename: Doekele G
authors.initials: DG
authors.lastname: Stavenga
mesh_terms: D046708:Amazona / Q000033:anatomy & histology / Q000378:metabolism*; D000818:Animals; D003116:Color; D005241:Feathers / Q000033:anatomy & histology / Q000378:metabolism*; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D010860:Pigments, Biological / Q000378:metabolism*; D013499:Surface Properties; D014796:Visual Perception
chemical_list: D010860:Pigments, Biological
keywords: barbs; barbules; melanin; thin films; vision