Bird personalities: the Great Tit
Over recent years, scientists have become increasingly interested in the personalities of birds and their go-to species has, more often than not, been the easy-to-study Great Tit. Great Tits can’t be asked to fill out a questionnaire or to undertake a psychometric test, and so their personalities have been inferred from their outward behaviours. Individual Great Tits have been classed as fast, slow or intermediate speed explorers by researchers since this correlates positively with, amongst other things, aggressiveness, boldness and risk-taking. Personality has been found to be repeatable in individual Great Tits and heritable within families, and does not appear to be determined by age, body condition or sex.
Under different environmental conditions, it seems that opposing personality traits can be beneficial. For example, in years when beechmast – an important winter food source for Great Tits and other birds – is abundant, thereby relaxing competition between Great Tits during winter but increasing competition for breeding territories in the spring (e.g. due to high survival rates), fast exploring adult males and slow exploring adult females tend to have the highest survival rates. The opposite has been found in years when beechmast is less abundant. So, why does this happen?
Because female Great Tits are subordinate to males in winter feeding flocks, being an aggressive, fast explorer is likely to be most beneficial for females when winter food is scarce. Males have better access to food than females, but after a good mast year when there are lots of rival males competing for territories, being a fast exploring male is likely to be most beneficial. It is not yet clear, however, why fast exploring adults of either sex experience lower survival rates than slow exploring adults in some years. Clearly, there is a cost to being a fast explorer, the nature of which requires more research.
In some years, then, it pays to be an aggressive, fast exploring bird while in others it does not. This variability certainly promotes, if not fully explains, the preservation of different personality types within Great Tit populations. Interestingly, Great Tits with intermediate personality types have been found, on average, to have both the greatest breeding success and highest life expectancy – so perhaps being somewhere in the middle is best!