Background One of the most challenging tasks in wildlife conservation and management is clarifying which and how external and intrinsic factors influence wildlife demography and long-term viability. The wild population of the Crested Ibis (Nipponia nippon) has recovered to approximately 4400, and several reintroduction programs have been carried out in China, Japan and Korea. Population viability analysis on this endangered species has been limited to the wild population, showing that the long-term population growth is restricted by the carrying capacity and inbreeding. However, gaps in knowledge of the viability of the reintroduced population and its drivers in the release environment impede the identification of the most effective population-level priorities for aiding in species recovery. Methods The field monitoring data were collected from a reintroduced Crested Ibis population in Ningshan, China from 2007 to 2018. An individual-based VORTEX model (Version 10.3.5.0) was used to predict the future viability of the reintroduced population by incorporating adaptive patterns of ibis movement in relation to catastrophe frequency, mortality and sex ratio. Results The reintroduced population in Ningshan County is unlikely to go extinct in the next 50 years. The population size was estimated to be 367, and the population genetic diversity was estimated to be 0.97. Sensitivity analysis showed that population size and extinction probability were dependent on the carrying capacity and sex ratio. The carrying capacity is the main factor accounting for the population size and genetic diversity, while the sex ratio is the primary factor responsible for the population growth trend. Conclusions A viable population of the Crested Ibis can be established according to population viability analysis. Based on our results, conservation management should prioritize a balanced sex ratio, high-quality habitat and low mortality.

Post-release dispersal of reintroduced animals refers to the process of successful colonization and failed settlement. To ensure the establishment and persistence of a reintroduced population, the impacts of different factors on the post-release dispersal of captive-bred animals must be assessed. In this article, we focused on two reintroduced Crested Ibis (Nipponia nippon) populations in Shaanxi Province, China. We applied multiple approaches to evaluate the effects of age, body weight, sex, timing of release, size of acclimatization cages for rewilding, and duration of acclimatization on the survival rate of released populations. The results showed that the survival capacity of released individuals was negatively correlated with their age in Ningshan County (Spearman, r = −0.344, p = 0.03, n = 41). The released ibises in Ningshan and Qianyang County had an average dispersal direction of 210.53 AE 40.54 (Rayleigh's z test: z = 7.881 > z 0.05 , p < 0.01, n = 13) and 27.05 AE 2.85 (Rayleigh's z test: z = 5.985 > z 0.05 , p < 0.01, n = 6), respectively, suggesting that the dispersal tended to clump in one direction in both sites. The MaxEnt modeling results indicated that the most significant environmental factor responsible for breeding site selection in Ningshan County was paddy field. In Qianyang County, precipitation affects nest site selection through influencing food availability. In conclusion, the evaluation framework used in this study can serve as an example for developing conservation priorities on the landscape scale for more animal reintroductions.

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