Dual Utility of a Melanin‐Based Ornament in Bearded Tits

A general mechanism to account for the maintenance of sexually selected traits is the armament–ornament model, which predicts that females exploit signals used in male–male aggressive contests. Melanin‐based ornaments are good candidates to be dual utility traits because they are usually involved in male–male competition and function as signals of male dominance or fighting ability. Despite this, very few studies have investigated the dual utility of melanin‐based plumage traits and results remain generally ambiguous. In this study, we investigated the dual function of a melanin‐based trait (the black beard) in the male bearded tit, Panurus biarmicus. In a controlled aviary experiment, beard length was the best predictor of dominance in male–male competition. In a choice experiment, females showed a proximity preference for males whose beard length was experimentally elongated. Our results indicate that beard length plays an important role in both male–male competition and female choice in bearded tits, as proposed by the dual utility model.