From reintroduction to extinction risk: Past, present and future of the newly established population of ospreys in southern Iberia

Biodiversity is declining due to ongoing environmental global change, and birds of prey are among the most threatened animal taxa. To counteract their decline, raptors have frequently been the focus of reintroduction programs worldwide. However, newly established populations must be continuously monitored to assess both short- and long-term persistence. In this work, we investigate the case of the osprey ( Pandion haliaetus ) in southern Spain, a cosmopolitan species formerly extirpated as a breeder from the western Mediterranean in the late 20th century. We used a long-term demographic and reproductive dataset (2003–2024) from the reintroduced population to investigate historical trends and long-term future population viability by using stochastic simulations for population dynamics. The population increased from zero territorial pairs in 2003 to 19 in 2024. We detected three phases in the evolution of the population: establishment (2003–2008), expansion (2009–2015), and stabilization (2016–2024). During the study period, annual productivity averaged 1.09 ± 0.32 juveniles (mean ± SD), breeding success 79.7 ± 13.6%, and clutch size 2.20 ± 0.75 eggs. Our baseline stochastic simulations—assuming current reproductive and demographic parameters (‘do-nothing scenario’)—suggests that ospreys from southern Spain face a high probability of extinction (47%) over the simulated horizon (40 years), driven by negative population growth. Population dynamics of the species were especially sensitive to changes in age-specific mortality rates—particularly those of adults, breeding performance, and age of first reproduction. These findings highlight the disproportional vulnerability of small populations of long-lived birds to slight environmental changes as these can easily translate into variations in key demographic and reproductive parameters. Specifically, they underscore the urgent need for post-reintroduction management to secure the self-sustainability of the Iberian population of ospreys, which could represent a potential source of genetic and demographic exchange within the vulnerable Mediterranean metapopulation.