Gouldian finches, Erythrura gouldiae, are an extraordinarily colourful species of passerine bird endemic to subtropical woodlands of northern Australia. Both sexes are brightly coloured with red, green, black, yellow, red and purple markings, it is for this reason that they are also sometimes known as rainbow finches.
In the wild the birds exhibit two main head colour morphs, black and red. There is also a rare yellow colour morph as shown in the image above. Interestingly, studies of captive birds have shown that males with red heads are on average more aggressive than those with black heads and that females have a preference for red-headed over black-headed individuals. Red headed males were also found to have higher levels of testosterone and corticosterone than black headed males when faced with socially challenging situations.
What this suggests is that behavioural characteristics, such as aggression and other traits, may be correlated with particular head colour morphs meaning that head colour is indicative of different personality types. This idea has been tested in a new paper by Leah Williams and her colleagues.
In order to determine if head colour really does indicate personality traits in Gouldian finches Williams and her colleagues tested a number of predictions. First they looked at pairs of black-headed birds which were expected to show less aggression towards each other than pairs of red-headed birds, this makes sense since red-headed birds had previously been found to exhibit higher levels of aggression.
The second prediction was that red-headed birds should be bolder, more explorative and take more risks than black-headed birds. This hypothesis is based on previous studies of other species that have shown a correlation between aggression and these behavioural characteristics. However, there is another possibility, red-headed birds could take fewer risks for two reasons; first, they may be more conspicuous to predators due to their bright colouration and second, it may pay black headed birds to take more risks and be more explorative so they find food resources before the dominant red-headed birds do.
In order to test the first prediction paired birds of matching head colour were moved into an experimental cage without food. After one hour of food deprivation a feeder was placed into the corner of the cage where there was only enough room for one bird to feed at a time. aggressive interactions such as threat displays and displacements were then counted over a 30 minute period.
The results as shown in the figure below were striking. Red-headed birds were significantly and consistently more aggressive than black-headed birds.
To test the birds willingness to take risks they were deprived of food for one hour before their feeder was replaced. After the birds had calmly begun to feed a silhouette of an avian predator was moved up and down in front of the cage to scare the birds from the feeder. The time it took for them to return to the feeder was taken as a measure of their willingness to take risks, birds that returned quickly were considered to be greater risk takers than those that were more cautious.
This time the results were surprising. Red-headed birds were considerably more cautious than those with black heads at returning to the feeder after a “predator” had been introduced. As the figure below shows they took on average 4x longer to begin feeding again than the less aggressive black-headed birds.
Finally, the authors investigated the birds interest in novel objects or “object neophilia” which is defined in the paper as “exploration in which investigation is elicited by an object’s novelty“. To do this a bunch of threads was placed on a perch within the cage, the time taken for the birds to approach the threads within one body length and to touch them were recorded over a one hour period. In line with the results from the risk taking experiment it was found that the aggressive red-headed birds showed less interest in novel objects than did black-headed birds. The difference is not so striking as the previous experiments but was statistically significant nonetheless.
These experiments were repeated after a two month interval and showed that different birds differed in their responses but the responses of individual birds were consistent over time. Head colour was found to predict the behavioural responses of the birds. Red-headed birds were more aggressive than black-headed birds but took fewer risks and were not explorative.
What is surprising about these results is that aggression does not correlate with risk taking behaviour, however, the authors do provide a convincing explanation, suggesting that…
…red coloration has been found to be conspicuous against natural backgrounds, and more conspicuous birds have been found to suffer higher predation rates. Thus, selection could favour more conspicuous red-headed birds taking fewer risks.
Interestingly boldness and risk taking behaviours were found to be strongly correlated, regardless of head colour they always occurred together forming a “behavioural syndrome”. This implies that there is selection in favour of specific combinations of traits and of head colour in relation to those traits. Selection favours aggression in red-headed birds and the boldness/risk taking behavioural syndrome in black-headed birds. This makes sense when you consider the high risk of predation faced by red-headed birds if they take too many risks and the need for black-headed birds to find food away from the dominant red heads which occupy the safest foraging locations.
Williams and her colleagues suggest that if red-headed birds are aggressive, and black-headed birds take more risks, this could lead to differences in foraging tactics. For example, black headed birds could increase their foraging opportunities by feeding at more risky sites away from interference by the dominant red-headed birds which feed in safer locations. The lower conspicuousness of their black heads means they are at less risk of predation at exposed sites that red-headed birds would be.
The results of this fascinating study strongly support the hypothesis that head colour does indeed signal personality in Gouldian finches. I would love to see some more research in this area. The authors themselves suggest that more research is needed to find out what roles head colours play in social situations. It would also be interesting to find out how widespread this phenomenon is, given that birds frequently use plumage colouration as signals it seems likely to me that colour may indicate personality in other avian species.
Williams L.J., King A.J. & Mettke-Hofmann C. (2012). Colourful characters: head colour reflects personality in a social bird, the Gouldian finch, Erythrura gouldiae, Animal Behaviour, 84 (1) 159-165. DOI: 10.1016/j.anbehav.2012.04.025