Social Group Membership With Residents Mediates Reinforcement Outcomes for a Translocated Bird

Animals released as part of reintroduction programmes are expected to benefit from social interactions with conspecifics from earlier releases, but empirical evidence is lacking. Using high-resolution GPS tracking across a population of bush stone-curlews (Burhinus grallarius), we investigated whether newly released animals ('reinforcers') interacted with previously released conspecifics ('residents'), and whether these interactions influenced post-release establishment. Post-release outcomes for reinforcers varied with social group membership. Half the reinforcers integrated into the residents' social group and the other half did not. Reinforcers in the residents' social group had greater release-site fidelity and faster roosting area establishment. Reciprocally, residents were attracted to the reinforcers, which enhanced resident roost-site fidelity. We recommend developing translocation tactics that leverage social relationships to improve post-release outcomes. These findings underscore the need to assess reinforcement outcomes at the population level, accounting for social dynamics between release cohorts.