Colourful characters: head colour reflects personality in a social bird, the Gouldian finch, Erythrura gouldiae

Remarkable diversity in behaviour and morphology (phenotypes) are often observed within a species; this diversity can be understood in terms of individuals maximizing their fitness. Based on evidence from studies linking different phenotypes to individual behaviours we hypothesize that discrete colour polymorphism can reflect personality. We tested for such a relationship in a social bird, the Gouldian finch, which shows two major head-colour morphs: red and black. Forty birds of differing head colours were used in five controlled laboratory tests. We found that three of the five tests were repeatable over time, and that bird performance in these tests differed with respect to head colour. Specifically: (1) pairs of red-headed birds were more aggressive than pairs of black-headed birds; (2) black-headed birds approached and touched a novel object quicker than red-headed birds (they were bolder); (3) black-headed birds returned to feed faster following the presentation of a false predator (they were less risk-averse); (4) boldness was positively correlated with risk taking (within the whole sample, within the red-headed birds and trending in the black-headed birds). Together, our results are consistent with our hypothesis that colour polymorphism could be indicative of consistent behavioural differences, and we make a number of predictions about how we expect this to function as a signal in competitive and cooperative (social) contexts.