Recreation negatively affects wildlife by influencing animal behaviour vital to reproduction and survival. Such non-consumptive effects of perceived predation risk are mainly studied in ground-breeding birds. However, if anti-predator responses characterize bird species generally, so should non-consumptive effects of perceived predation associated with human recreation. Moreover, as individuals consistently differ in behaviours linked to anti-predator responses, they should also differ in responses to recreation, with bolder birds being less affected. To test this key prediction, we quantified effects of human recreation pressure on a cavity-breeding passerine. We uniquely quantified human recreation pressure over a substantial (8-year) period within twelve nest-box populations of the great tit Parus major, assayed annually for reproductive parameters. We detected considerable spatial variation in recreation pressure. In plots with high recreation pressure, we found strong support for birds breeding further away from highly frequented paths and birds producing smaller clutches; we also found moderate support for birds producing fewer fledglings. These detrimental effects did not vary with behavioural proxies of an individual’s risk-taking phenotype (exploratory activity). This implies that effects of recreation pressure apply to the average bird, and extend to species (like forest birds) not previously considered.

Individual repeatability characterises many behaviours. Repeatable behaviour may result from repeated social interactions among familiar group members, owing to adaptive social niche specialisation. In the context of aggression, in species like field crickets, social niche specialisation should also occur when individuals repeatedly interact with unfamiliar individuals. This would require the outcome of social interactions to have carry-over effects on fighting ability and aggressiveness in subsequent interactions, leading to long-term among-individual differentiation. To test this hypothesis, we randomly assigned freshly emerged adult males of the southern field cricket Gryllus bimaculatus to either a solitary or social treatment. In the social treatment, males interacted with a same-sex partner but experienced a new partner every three days. After three weeks of treatment, we repeatedly subjected treated males to dyadic interactions to measure aggression. During this time, we also continuously measured the three-daily rate of carbohydrate and protein consumption. Individual differentiation was considerably higher among males reared in the social versus solitary environment for aggressiveness but not for nutrient intake. Simultaneously, social experience led to lower within-individual stability (i.e. increased within-individual variance) in carbohydrate intake. Past social experiences, thus, shaped both behavioural individuality and stability. While previous research has emphasised behavioural individuality resulting from repeated interactions among familiar individuals, our study implies that behavioural individuality, in the context of aggression, may generally result from social interactions, whether with familiar or unfamiliar individuals. Our findings thus imply that social interactions may have a stronger effect on individual differentiation than previously appreciated.

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