Many animals have signals of strength that they use to settle disputes. In the purple swamphen, more dominant birds have larger frontal shield ornaments, and we tested the link between this signal and the social environment with a unique experiment. Using a small amount of black paint, we made the shields of some individuals appear smaller than they actually were. We found that birds with experimentally reduced shield size were aggressively challenged by others. Additionally, birds with cosmetically reduced shields showed a decrease in their true shield size when we recaught them one week later, demonstrating that there is a dynamic link between signals and the social environment. This finding provided a key piece of evidence for the ‘integrative costs’ model of honest signaling.
Dey CJ, Dale J & Quinn JS. 2014. Manipulating the appearance of a badge of status causes changes in true badge expression. Proceedings of the Royal Society B: Biological Science. 20132680.