DOI: 10.5061/dryad.gxd2547h5
title: Spectral data for analysis: Full spectra colouration and condition-dependent signalling in a skin-based carotenoid sexual ornament

description: Carotenoid-based traits commonly act as condition-dependent signals of
 quality to both males and females. Such colours are typically quantified
 using summary metrics (e.g. redness) derived by partitioning measured
 reflectance spectra into blocks. However perceived colouration is a
 product of the whole spectrum. Recently, new methods have quantified a
 range of environmental factors and their impact on reflection data at
 narrow wavebands across the whole spectrum. Using this approach, we
 modelled the reflectance of red integumentary eye combs displayed by male
 black grouse (Lyrurus tetrix) as a function of ornament size and variables
 related to male quality. We investigated the strength and direction of
 effect sizes of variables at each waveband. The strongest effect on the
 spectra came from eye comb size, with a negative effect in the red part of
 the spectrum and a positive effect in UV reflectance. Plasma carotenoid
 concentration and body mass were also related to reflectance variance in
 differing directions across the entire spectra. Comparisons of yearlings
 and adults showed effects were similar, but stronger on adult reflectance
 spectra. These findings suggest reflectance in different parts of the
 spectrum are indicative of differing components of quality. This method
 also allows a more accurate understanding of how biologically relevant
 variables may interact to produce perceived colouration and
 multi-component signals, and where the strongest biological effects are
 found.
description: <b>Eye comb size and
 reflectance </b> Eye comb size was calculated by
 first taking a digital video recording of both eye combs against a scale
 for each individual. Left and right eye comb areas
 (cm<sup>2</sup>) were measured using ImageJ (Rasband 2012).
 Comb reflectance was calculated in the field using spectrophotometry
 (Ocean Optics USB2000) over the range of 320-700nm (Figure 2; Cuthill
 2006, Montgomerie 2006, see Siitari et al. 2007 for methods in full
 detail). Reflectance was measured by placing the probe perpendicularly
 against the eye comb at a distance of 12mm from the surface. The strobe
 illumination area encompassed an area measuring approximately 1.5mm in
 diameter. This was replicated twice per comb side, varying the probe
 position and side (left or right) measured on each repetition. After every
 four measurements, a 99% white standard (LabSphere) was used to
 recalibrate the spectrophotometer.<b> </b>Sometimes,<b>
 </b>the spectrophotometer recorded negative values especially at
 &lt;380nm – negative values were excluded as these were obvious probe
 errors.    <strong>Other
 variables</strong> For other condition measures,
 please see the paper for a detail description of each
 variable. <strong> </strong>
description: There are two sheets. Sheet 2 contains a description of each
 column header and any associated notes. If something is not clear, I am
 happy to help. Please note that these data are also submitted to FigShare
 (the same file).