DOI: 10.5061/dryad.1rp0s
title: Data from: The effects of life history and sexual selection on male and female plumage colouration

description: Classical sexual selection theory provides a well-supported conceptual
 framework for understanding the evolution and signalling function of male
 ornaments. It predicts that males obtain greater fitness benefits than
 females through multiple mating because sperm are cheaper to produce than
 eggs. Sexual selection should therefore lead to the evolution of
 male-biased secondary sexual characters. However, females of many species
 are also highly ornamented. The view that this is due to a correlated
 genetic response to selection on males was widely accepted as an
 explanation for female ornamentation for over 100 years and current
 theoretical and empirical evidence suggests that genetic constraints can
 limit sex-specific trait evolution. Alternatively, female ornamentation
 can be the outcome of direct selection for signalling needs. Since few
 studies have explored interspecific patterns of both male and female
 elaboration, our understanding of the evolution of animal ornamentation
 remains incomplete, especially over broad taxonomic scales. Here we use a
 new method to quantify plumage colour of all ~6,000 species of passerine
 birds to determine the main evolutionary drivers of ornamental colouration
 in both sexes. We found that conspecific male and female colour
 elaboration are strongly correlated, suggesting that evolutionary changes
 in one sex are constrained by changes in the other sex. Both sexes are
 more ornamented in larger species and in species living in tropical
 environments. Ornamentation in females (but not males) is increased in
 cooperative breeders—species in which female–female competition for
 reproductive opportunities and other resources related to breeding may be
 high. Finally, strong sexual selection on males has antagonistic effects,
 causing an increase in male colouration but a considerably more pronounced
 reduction in female ornamentation. Our results indicate that although
 there may be genetic constraints to sexually independent colour evolution,
 both female and male ornamentation are strongly and often differentially
 related to morphological, social and life-history variables.
description: Plumage coloration in
 passerine birdsPlumage colour scores
 (N=5831 species) and predictor variables (N = 2471 species) in passerine
 birds. This data set includes plumage scores for males and females as
 calculated from RGB (red, green, blue) values measured from plates in the
 Handbook of the Birds of the World (see text of article for details).
 Additionally we include the values of the 5 key predictor variables: 1)
 body size (first phylogenetic principle component (PPC1) of body mass and
 wing length), 2) tropical life history (PPC1 of latitude, seasonality and
 clutch size), 3) sexual selection (PPC1 of mating system, sexual size
 dimorphism and paternal care), 4) cooperative breeding (no = 0 and yes =
 1) and 5) migration (none = 0, partial = 0.5 and complete = 1). All
 predictor variables were scaled to a mean = 0 and standard deviation = 1.
 These variables were used in the multiple predictor phylogenetic
 generalized least squares model, Markov Chain Monte Carlo generalized
 linear mixed models and phylogenetic controlled d separation path analysis
 (Table 1b, Figure 4 and Figure 5 of the article respectively). Scientific
 names, English names and TipLabels correspond to the phylogenetic trees
 provided by www.birdtree.org (Jetz, W., Thomas, G., Joy, J., Hartmann, K.,
 & Mooers, A. 2012. The global diversity of birds in space and time.
 Nature, 491(7424), 444-448).plumage_scores.csv