Translocation outcomes for mobile species can be affected by post-release movement of individuals, yet few population reintroduction and supplementation projects consider propensity to move as a selection criterion when selecting individuals to release or sites for release. We investigate the influence of release age (juvenile or subadult), the size of the release group and the size of the wild population at the release site on movements of Critically Endangered kaki (black stilt) Himantopus novaezelandiae. Over 460 subadult and juvenile kaki have been released during 12 years at nine sites in the Waitaki Basin, New Zealand, with the aim of supplementing specific sub-populations. Among the survivors that reached breeding age, 32% of released kaki ended up away from their release sites, i.e. away from the subpopulations they were intended to augment and 15% of these birds were in unmanageable areas where monitoring cannot take place. Kaki released as juveniles (2–3 months) made more long moves and moved further from the release site during 2 months post-release. The presence of conspecifics affected behaviour after release: released birds were more likely to remain closer to the release site when the size of the wild population at the release site was large, and kaki released in larger groups were more likely to make more longer moves. Despite initial differences in mobility, long-term monitoring revealed equal proportions of 2-year old survivors that had been released as juveniles and subadults returning and being observed consistently at release sites, emphasizing the value of long-term monitoring in informing release strategies for population restorations.