Illustration of sexual differences in colouration for 398 parrot species. (a) Distribution of the sexual dichromatism score and (b) distribution of sexual differences in colour elaboration. X‐axes scales are log₁₀ transformed and log₁₀‐modulus transformed (sign(x)*log10(abs(x)+1), John & Draper, 1980) for negative values. Illustrations in each panel represent the species that have the minimum and maximum scores for each variable. Shown are box plots with median (vertical line) and interquartile range (box), and violin plots (grey lines) showing the probability density of the data. Illustrations © Lynx Edicions