title: A closer look at the feather coloration in the male purple sunbird, Nectarinia asiatica.
abstract: During the breeding season male, but not female, individuals of the purple sunbird possess colourful plumage of chiefly blue and black coloration with a splatter of orange and yellow on the chest. Representative feathers of these colours were collected from male birds during the breeding season and analyzed by reflectance and scanning electron microscopy. The rachis, which is the central support of a feather on which various barbs and barbules are arranged, is spongy and made up of keratin layers with rod-shaped melanosomes sparsely distributed within these layers. Barbs and barbules are the structural units of the feather and depending on how they are arranged provide a characteristic shape to the feather. X-Ray diffraction (XRD) analyses of the feathers revealed the presence of various metal elements that might contribute to the feathers' colorations. Blue feathers are iridescent and contain mainly iron, copper, zinc and cobalt (in that order of abundance); black feathers were also found to contain mainly iron and copper, but chromium instead of zinc and cobalt, while yellow feathers were found to contain predominantly cobalt and nickel. The metal content of the feathers in an as yet unknown way may be involved in the production of the distinct absorbance and reflectance patterns that the brilliant plumage of the purple sunbird is renowned for.
authors.affiliation: Department of Life Science, National Institute of Technology-Rourkela, Rourkela, 769008, India.
authors.forename: Biswa Bhusana
authors.initials: BB
authors.lastname: Mahapatra
authors.affiliation: Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, Rajasthan, 333031, India.
authors.forename: Sandhya Amol
authors.initials: SA
authors.lastname: Marathe
authors.affiliation: Research Institute of Luminous Organisms, Nakanogo, Hachijojima, Tokyo, 100-1623, Japan.
authors.forename: Victor Benno
authors.initials: VB
authors.lastname: Meyer-Rochow
authors.affiliation: Department of Life Science, National Institute of Technology-Rourkela, Rourkela, 769008, India. Electronic address: mishramo@nitrkl.ac.in.
authors.forename: Monalisa
authors.initials: M
authors.lastname: Mishra
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005241:Feathers / Q000737:chemistry* / Q000648:ultrastructure; D005260:Female; D007633:Keratins / Q000032:analysis; D008297:Male; D008670:Metals / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry / Q000648:ultrastructure; D046109:Passeriformes / Q000033:anatomy & histology*; D010858:Pigmentation; D014961:X-Ray Diffraction
chemical_list: D008670:Metals; D007633:Keratins
keywords: Feather coloration; Metal trace elements; Optical microscopy; Scanning electron microscopy; Structural coloration; Sunbird