Personality composition affects group cohesion of homing pigeons in response to novelty and predation threat

Understanding how and why animal groups behave collectively is a central question in behavioural and social sciences. Variation in the phenotypic composition of the individuals within a group can lead to differences in group attributes and performance. However, whether and how individual personalities translate into group performance is not yet fully understood because experiments that test such hypotheses in realistic set-ups are still scarce. We explored how between-group variation in personality composition affected flock cohesion during homing flights of homing pigeons, Columba livia. Based on consistent individual differences, we established flocks of either ‘more reactive’ (MR flocks) or ‘less reactive’ (LR flocks) pigeons naïve to homing. Cohesion of flocks was tested in three distinct challenges: (1) first-ever collective homing experience (novelty); (2) release from a novel site (novel site homing); and (3) hunt by a robotic peregrine falcon (predation threat), with the latter two challenges performed with flocks trained for homing. MR flocks were more cohesive than LR flocks in the novelty challenge, but showed similar levels of cohesion during the novel site homing challenge. Predation threat decreased cohesion in both flock types, with a stronger effect in LR flocks. These results indicate that differences in the composition of personalities of group members can produce detectable differences in collective performance, and highlight the importance of accounting for individual-level behavioural variation when studying collective patterns in nature.