Spectral data for analysis: Full spectra colouration and condition-dependent signalling in a skin-based carotenoid sexual ornament

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 i...