The effects of ecology and behaviour on the evolution of colouration in Coraciiformes

<p>What drives the evolution of plumage colour in birds? Bird colour is likely to be under both natural and sexual selection where natural selection may favour evolution towards crypsis or camouflage whereas sexual selection may favour evolution towards conspicuousness. The responses to selection are predicted to relate to species' ecology, behaviour, and life history. Key hypotheses have focused on habitat and light environment, breeding strategy, territoriality, and hunting behaviour. We tested these potential causes of colour variation in the Coraciiformes, a colourful clade of non-passerine birds, using phylogenetic comparative methods and data on plumage colouration and brightness measured from museum specimens. We found that correlates of colour evolution in Coraciiformes vary across body regions and depend on the focal colour property (hue or brightness). While light environment showed widespread effects on colouration in multiple body regions for both hue and brightness, selection pressures related to behavioural characteristics had more spatially localized effects (e.g. territoriality on wing feather brightness and hunting strategy on belly hue). Our results reveal both general patterns that may hold across other bird clades and more nuanced effects of selection that are likely to be mediated through the visual ecology of the signaller and receiver and the behavioural characteristics of Coraciiform species. </p>