The last remaining population of the Crested Ibis Nipponia nippon in the wild was studied in the Qinling Mountains, Yangxian County, Shaanxi Province, central China, over 24 breeding seasons with particular attention being paid to the nesting behaviour and breeding success. The average clutch size varied significantly among years (2.84 ± 0.77; n = 271), suggesting that food abundance, which was distinct in different areas, was indeed a limiting factor. The mean hatching success was 80.2%, and ranged from 35.7% to 100%. Egg losses were due to three reasons: infertility or the eggs being addled, predation, and human disturbance. Three reasons accounting for chick death were highlighted: shortage of food, predation, and disturbance from local inhabitants. However, the overall breeding success of the Crested Ibis, which averaged 65.6%, was much higher than that of many nidicolous birds and was clearly dependent not only on the stability of pair maintenance but also on human conservation and protection measures. The relatively higher proportion of unsuccessful nests at altitudes between 500–700 m and 701–900 m was linked with the more frequent human activities, predation and lower stability of nest-trees in such areas. The fact that there was no significant variation in the number of successful nests or breeding success across different altitudinal zones demonstrated that, to a large degree, habitats used by the Crested Ibis were now suitable for breeding. The rapid increase in the species' numbers in recent years has been achieved through effective protection measures, including legislation, management of population and habitat, and regular surveys and monitoring. A reintroduction programme has been put into effect, protecting the population from a chance catastrophe such as communicable diseases within its limited range.
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