| Reintroduction projects attempt to re-establish a self-sustaining population for endangered species within their historical ranges, usually through the release of captive-bred or wild-caught individuals into the wild. Reintroduction is a frequently used tool in the conservation of endangered species. Due to the high financial costs and low success rate, rigorous assessment of feasibility is essential prior to implementation as well as appropriately long post-release monitoring to assess success. Although the aim of a reintroduction is to establish a free-living, self-sustaining population, the progress of a reintroduction comprises a sequence of objectives, including the survival of released individuals, breeding by released individuals in the wild and then subsequent growth and persistence of the population. Each of these stages should be assessed by appropriate method and the importance of post-release monitoring has been emphasized in assessing progress with reintroduction projects. In many cases, even today, monitoring is found to be inadequate to appropriately assess success or failure.The Crested Ibis (Nipponia Nippon) is one of the world’s endangered species. The intensive conservation work has been carried out both at home and abroad since the rediscovery of wild population in 1981. After 30 years of protection, wild population expanding, captive breeding population has reached more than 1,000. Now there is only one wild population remaining in the world, it has been suggested that the captive-bred individuals of the Crested Ibis should gradually be reintroduced to other parts of its former range in China, as the wild population is currently vulnerable to extinction through a chance catastrophe within its limited range. After pre-surveys on potential release site in 9 provinces in China, the Ningshan County was confirmed the first reintroduction area. Hence, the world’s first Crested Ibis reintroduction project implemented in Ningshan County, May 2007. A total of 56 individuals were successively released to wild between 2007 and 2011 and long-term post-release monitoring has been continuing after release.In order to orient and adjust future management activities, predicting whether it is a sustainable population, we here assess the initial reintroduction program in Ningshan County for the endangered Crested Ibis by analyzing post-release monitoring data, evaluating demographic parameters (survival, breeding success), then compared the results with published data on wild Crested Ibis population. Survival was estimated by Cormack-Jolly-Seber model (CJS model), survival of different age groups was estimated by Live-Recovery model. Breeding success, age structure and sex ratio were also calculated among 2008-2014.Our results indicated that:(1) The first year survival of released individuals was 57.1%, eatimated average annual survival of 56 released Crested Ibis by CJS model was 0.769±0.074 and varied among years (t=10.406,P=0.000, df=6); (2) Estimated survival of wild born adults and nestlings was 69.3% and 48.1%, respectively by Joint Live and Dead Encounters model (LD model); (3) Clutch size of reintrodued population was 3.22±0.84 (n=46) with no signigicant variation among years (F=0.765, df=6, P=0.602), while wild population was 2.84±0.77 (n=271); (4) Hatching success was 69.1%, and varied significantly among 7 years (F=2.481, P=0.040,df=6), loss of egges are mainly due to infertile eggs and predation by predators such as King Rat Snake (Elaphe carinata), fledging success of nestlings was 73.6%(57.1%-84.6%), death of nestlings were caused by nature, predation and abanonment by parents; (5) breeding success (52.5%) of reintroduced population was lower than wild population (67.6%); (6)There is a siginificant correlation bewtween hatching success and breeding success (r=0.847, P=0.016<0.05), fleging success of nestlings was obviously related to breeding success (r=0.910, P<0.004<0.05); (7) Among the 40 individuals we investigated, the proportion of pre-breeding Crested Ibis (0-2 yr) was 42.5%, individuals among breeding age (>2 yr) was 50%. Number of female was 22, male 18 and the sex ratio was 55%.By comparing relevant data of reintroduced population with wild population and Japanese reintroduced population, we assume that that our reintroduced population is self-sustainable based on the survival and fecundity data. Although breeding success of reintroduced population is relatively lower than wild population, it may be increase with the increase of more offspring involved in breeding. Thus, population size would increase and be self-sustaining without any additional release.The conclusion of this study mainly include:(1) The achievement of the initial reintroduction project of Crested Ibis in Ninshan County, Shaanxi Province is an good example for subsequent release of this species. (2) A successful reintroduction requires suitable habitat, founder population size no less than twenty and soft release may help the individuals adapt to the environment as soon as possible. (3) The formation of satellite population facilitates gene exchange among small population and associates reintroduced population with wild population, it shows that the releae stocks have adapt to the environment and present similar behavior pattern with source population. (4) Dependment on provisioning may be the cause of released individuals stay at release site, so food supplement in breeding and wandering stage may guarantee more Crested Ibis to survive. (5) For the Crested Ibis who have no obvious territory behavior, continued release at one site can contribute to later released individuals learn survive skills from former released individuals as well as formation of new breeding pairs. If possible, birds that have previously bred in captivity should be considered firstly. |
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