Spectral reflectance and directional properties of structural coloration in bird plumage.

Osorio, D and Ham, A D (2002) Spectral reflectance and directional properties of structural coloration in bird plumage. Journal of Experimental Biology, 205. pp. 2017-2027. ISSN 0022-0949

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Abstract

Bird plumage is coloured both by pigments and by spectrally selective interference in the light reflected from feather barbs. These barbs are composites of high- and low-refractive-index materials, and light is reflected at refractive index boundaries. The spatial structure determines the wavelengths where constructive interference occurs and, hence, the spectral tuning. The spectral tuning of interference colours often varies with angles of illumination and reflection, which produces iridescence. Iridescence and other optical effects mean that interference coloration looks different from pigmentation and is visually striking. To study the optical and visual properties of structural plumage colours, we recorded the reflectance spectra of feathers and in particular their directional properties. A fixed spot on a feather was viewed from a fixed position, whilst the feather orientation and the angle of illumination were varied. We recognise two main types of coloration, `directional' and `diffuse'. Within these types, there is considerable variation, and five examples illustrate some features of structural plumage colours and suggest how their optical and visual properties can be measured and described.

Item Type: Article
Schools and Departments: School of Life Sciences > Evolution, Behaviour and Environment
Depositing User: Daniel ColacoOsorio
Date Deposited: 06 Feb 2012 19:58
Last Modified: 21 Mar 2012 11:53
URI: http://sro.sussex.ac.uk/id/eprint/23340
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