Risk and Effectiveness in the Use of Agonistic Displays By American Goldfinches

Abstract

Abstract In aggressive contests over access to feeders, American goldfinches (Carduelis tristis) appeared to be using displays based on their risk and effectiveness. Display types varied in both their effectiveness and the risk of their use. The effectiveness of using a display was positively related to the risk of using that display. When the value of the resource under dispute was increased individuals used more of the riskier yet more effective displays. Associated with the increased use of the riskier displays was a greater number of encounters ending in fights. Individuals also used each display type with different frequency depending on the relative dominance status of their opponent. Bluffing may have been kept at low levels among the goldfinches by the ease of detecting bluffing, due to individual recognition, and by the costs of being detected.