A bird’s-eye view reveals no fixed differences in plumage coloration between divergent populations of Painted Buntings

Abstract In birds, the process of speciation is closely associated with transitions in ornamentation, including coloration, plumage pattern, and song. To investigate the origins of these shifts and their connection to genetic changes, we conducted a study on one of the most highly ornamented songbirds, the Painted Bunting ( Passerina ciris ). The male Painted Buntings exhibits a stunning array of colors, with a red chest, blue head, green back, green coverts, and pink rump. In addition, Painted Buntings show a high level of genetic structure, with eastern and western populations that have fixed genetic differences in both nuclear and mitochondrial genes. Using non-invasive spectrophotometry techniques, we measured the coloration of six plumage patches on 88 museum specimens of male Painted Buntings in definitive plumage from across the range of the species. We predicted that there would be divergence between the genetically distinct eastern and western populations in ornamental coloration that is perceptible to a bunting but imperceptible to a human observer. However, we measured no consistent nor substantial difference in the plumage coloration of males from different populations. The observation of substantial divergence in nuclear and mitochondrial genotype with no change in ornamental coloration between populations of a brightly colored bird has important implications for the role of sexual selection in the process of speciation.