The role of the epaulets of the male Red-winged blackbird, Agelaius phoeniceus, was examined. Territorial male Red-wings were captured and their epaulets blackened with Nyanzol D, a permanent black dye. The following results were obtained: 1) Sixty-four percent of the males with black epaulets lost their territories while only eight percent of the control males lost theirs. 2) Males with epaulets blackened prior to pair formation were still able to "attract" females and mate successfully. It was concluded that the epaulets communicate threat between rival males but that they have little if any role in intersexual encounters. The epaulets, therefore, have probably evolved in response to intrasexual (epigamic) selection pressure.