Résumé
Avian plumage colouration is an iconic example of trait variability among
species. Sexual, social, and natural selection, and the environmental
variables modulating them, may explain this variability. So far, most
research exploring environmental effects on the variability of plumage
colouration has focused on the variation in overall plumage darkness.
Research on other aspects of colour variation, such as the diversity of
colours exhibited by a species (i.e., colour complexity), is limited and
has provided inconsistent results. Besides, colour complexity has mostly
been analysed at the whole plumage level, despite the possibility that
different plumage patches may be sensitive to different environmental
factors. Here, we quantify male and female coloration in 58 species of the
family Paridae, and use multi-predictor Bayesian phylogenetic mixed models
to estimate the relationship of coloration with environment and certain
species-specific characteristics. We consider both the colouration of the
whole body and the coloration of four separate colour patches (head,
chest, back, and wing). We find that Paridae species in climates
with greater seasonality and intermediate temperatures present more
complex colouration than do species in other climates. In addition, males,
relatively small species, and species with relatively greater sexual
dichromatism have more complex plumage colouration than otherwise. We find
that the numbers of predators and sympatric conspecifics are more
associated with female coloration than with male coloration. Finally, the
strength of associations with colour complexity are specific to each
plumage region: species recognition, beak shape, and climate variables
related to competition for reproductive resources (i.e. seasonality of
temperature and precipitation), are more strongly associated with
colouration complexity of the head and breast than with that of the back
and wing. Overall, our results illustrate the importance of
climatic and social variables, the link between colour complexity and
dichromatism in both sexes, and the analysis of distinct plumage areas for
understanding global patterns of colouration complexity and the processes
that promote them.