Differences in plumage coloration between ventral and dorsal regions on Atlantic Forest birds

Plumage coloration is an important trait for communication signalling and camouflage, enabling birds to provide cues of health condition and avoid predators. Such coloration can differ among body regions, with some regions presenting conspicuous coloration, while others are more discreet. Plumage coloration can also be associated with species' life‐history traits, such as diet, habitat and nest type. Despite the relevance to ecology and evolution of bird plumage coloration, little is known regarding the relationship between the coloration of ventral and dorsal regions of bird species, especially in the Atlantic Forest, a global hotspot of biodiversity. Here we assessed plumage brightness and saturation of the dorsal and ventral regions of Atlantic Forest birds, and analysed the differences in coloration and colour variability between the regions. We also tested whether sex dichromatism, nest type, diet, habitat and foraging stratum preference are related to plumage coloration. We found that dorsal regions tend to be darker, more achromatic and less variable across species when compared to ventral regions. Additionally, plumage coloration of bird species incubating in open nests is brighter than in birds from closed nests, while species with sexual dichromatism tend to present darker ventral regions. Our results bring new insights into the role of plumage coloration in Atlantic Forest bird ecology, suggesting that different evolutionary forces may act in different body regions.