Plumage reflectance signals dominance in Florida scrub-jay, Aphelocoma coerulescens, juveniles

Abstract

Although sexual selection is undeniably important in the evolution and maintenance of ornamental traits, it remains an unsuitable explanation for juvenile ornamentation. Male–male competition has been important in the evolution of UV-blue plumage ornamentation in birds, suggesting that this type of plumage may signal status more generally. In the present study, we compared dominance status of juvenile Florida scrub-jays before and after experimental plumage manipulation and found that plumage reflectance signalled status. Male–male competition is important in maintaining UV-blue plumage ornamentation in adults of other species. However, our evidence shows that sexually dimorphic ornamentation can also mediate competition over food resources in juvenile Florida scrub-jays. Understanding status signalling among juveniles may yield insights into differences in fitness, especially in species with cohesive social systems where early interactions are likely to influence future competitions over resources or mates. ► We experimentally manipulated plumage reflectance of juvenile Florida scrub-jays. ► We compared dominance before and after plumage manipulation. ► We found that reducing plumage reflectance caused a reduction in dominance. ► We conclude that plumage reflectance signals status in juvenile Florida scrub-jays.