On the sustainability of a reintroduced Crested Ibis population in Qinling Mountains, Shaanxi, Central China

Reintroduction projects aim to reestablish a self-sustaining population of an endangered species within its historical range. Adequate post-release monitoring by gathering demographic data is important to evaluate the success of a reintroduction. Survival and reproduction rates of a reintroduced population can be compared with a self-sustaining wild population to evaluate the success of a reintroduction. In early 2007, Nipponia nippon (Crested Ibis) was reintroduced into the Qinling Mountains (Shaanxi, Central China). In this study, we attempt to evaluate the demographic status of the reintroduced population. Age-specific survival rates of 56 released adults and 77 wild-born fledglings were estimated using mark-recapture data obtained from 2007 to 2014. Survival rates for the yearlings (0.599, with 95% confidence interval [CI]: 0.467-0.719) were lower than the estimates from a wild population in Yangxian County, but the survival rates of the adults (0.678, with 95% CI: 0.603-0.745) were similar. The number of breeding pairs gradually increased since 2008, although breeding success (52.5%) was somewhat less than that of the wild population (67.6%). The stochastic estimation of population growth rate (1.084 with 95% CI: 1.069-1.098) and population size (5-fold increase) estimated from an age-classified Leslie matrix indicate that the reintroduced population of the Crested Ibis is more likely in regulation phase over the next 25 years. We conclude that the reintroduction of the Crested Ibis in Qinling Mountains has great promise, and progress toward a self-sustaining population has been made under some interventions. Governments, local communities, and scientists need to facilitate habitat restoration for the long-term survival of this endangered species.