Summary 1.Interest in the evolutionary origin and maintenance of individual behavioural variation and behavioural plasticity has increased in recent years. 2. Consistent individual behavioural differences imply limited behavioural plasticity, but the proximate causes and wider consequences of this potential constraint remain poorly understood. To date, few attempts have been made to explore whether individual variation in behavioural plasticity exists, either within or between populations. 3. We assayed 'exploration behaviour' among wild-caught individual great tits Parus major when exposed to a novel environment room in four populations across Europe. We quantified levels of individual variation within and between populations in average behaviour, and in behavioural plasticity with respect to (i) repeated exposure to the room (test sequence), (ii) the time of year in which the assays were conducted and (iii) the interval between successive tests, all of which indicate habituation to novelty and are therefore of functional significance. 4. Consistent individual differences ('I') in behaviour were present in all populations; repeatability (range: 0AE34-0AE42) did not vary between populations. Exploration behaviour was also plastic, increasing with test sequence -but less so when the interval between subsequent tests was relatively large -and time of year; populations differed in the magnitude of plasticity with respect to time of year and test interval. Finally, the between-individual variance in exploration behaviour increased significantly from first to repeat tests in all populations. Individuals with high initial scores showed greater increases in exploration score than individuals with low initial scores; individual by environment interaction ('I · E') with respect to test sequence did not vary between populations. 5. Our findings imply that individual variation in both average level of behaviour and behavioural plasticity may generally characterize wild great tit populations and may largely be shaped by mechanisms acting within populations. Experimental approaches are now needed to confirm that individual differences in behavioural plasticity (habituation) -not other hidden biological factorscaused the observed patterns of I · E. Establishing the evolutionary causes and consequences of this variation in habituation to novelty constitutes an exciting future challenge.

Polymorphisms in the dopamine receptor D4 gene (DRD4) have been related to individual variation in novelty-seeking or exploratory behaviour in a variety of animals, including humans. Recently, the human DRD4 orthologue was sequenced in a wild bird, the great tit (Parus major) and a single nucleotide polymorphism in exon 3 of this gene (SNP830) was shown to be associated with variation in exploratory behaviour of labraised individuals originating from a single wild population. Here we test the generality of this finding in a large sample of free-living individuals from four European great tit populations, including the originally sampled population. We demonstrate that the association between SNP830 genotype and exploratory behaviour also exists in freeliving birds from the original population. However, in the other three populations we found only limited evidence for an association: in two populations the association appeared absent; while in one there was a nonsignificant tendency. We could not confirm a previously demonstrated interaction with another DRD4 polymorphism, a 15 bp indel in the promoter region (ID15). As yet unknown differences in genetic or environmental background could explain why the same genetic polymorphism (SNP830) has a substantial effect on exploratory behaviour in one population, explaining 4.5–5.8% of the total variance—a large effect for a single gene influencing a complex behavioural trait—but not in three others. The confirmation of an association between SNP830 genotype and personality-related behaviour in a wild bird population warrants further research into potential fitness effects of the polymorphism, while also the population differences in the strength of the association deserve further investigation. Another important future challenge is the identification of additional loci influencing avian personality traits in the wild

Dispersal is a major determinant of the ecological and evolutionary dynamics of natural populations. Individuals differ greatly in the likelihood and distance of dispersal, but it is generally unclear to what extent intrinsic, possibly genetic, differences contribute. Here we present the first explicit empirical evidence for genetic coupling of local dispersal and exploratory behaviour, a key 'animal personality' trait. Using relatedness data from a multi-generation pedigree of free-living great tits (Parus major), we find quantitative genetic variation for both the distance of local dispersal within our study area and the rate at which individuals explore a novel environment. Moreover, we find a strongly positive genetic correlation between local dispersal distance and exploration rate, despite a weak and non-significant phenotypic correlation. These findings demonstrate a potentially important behavioural mechanism underlying heritable differences in local dispersal and highlight the potential for concerted evolution of dispersal and animal personality in response to selection.

Personality differences measured under standardized lab-conditions are assumed to reflect differences in the way individuals cope with spatio-temporal changes in their natural environment, but few studies have examined how these are expressed in the field. We tested whether exploratory behaviour in a novel environment predicts how free-living individual great tits (Parus major) react to a change in food supply. We temporarily removed food at feeding stations during two summers and recorded the behavioural response of juvenile birds to these food manipulations using radiotracking. When challenged by an abrupt change in food supply, fast-exploring individuals more rapidly switched to different foraging areas at longer distances from the feeder. This study is the first to show that personality traits predict the spatial response to experimentally induced changes in their natural environment.

A growing number of studies have shown that individuals differ consistently in a suite of correlated behavioural traits across various contexts and situations. Yet, most work on animal personalities has been performed under laboratory conditions and still little is known about the ecological significance of differences in personality in the wild, and the behavioural mechanisms underlying possible fitness consequences. In this study, we investigated individual differences in personality in relation to nest defence behaviour in wild great tits. Nest defence is an important aspect of parental care and involves a trade‐off between two fitness components (i.e. survival and reproduction). As a measure of personality we used exploratory behaviour in a novel environment as this has been shown to be correlated with several other behavioural traits including risk‐taking and aggression, two important behavioural components of nest defence. We found that the intensity of alarm calling towards a human intruder was positively associated with exploratory behaviour, while there was a negative association between exploration score and number of movements during nest defence. Thus, fast explorers are shown to respond more boldly towards predators in the field. More generally we show that individuals with different personalities vary in their anti‐predator and reproductive investment strategies.