Breeding Variation in a Reintroduced Crested Ibis Nipponia nippon Population in Central China

The crested ibis Nipponia nippon formerly occurred throughout East Asia, but since 1981 its unique population has been confined to a narrow band in transborder area of Yangxian, Chenggu and Xixiang County of Shaanxi Province, Central China, on the south slope of the Qinling Mountains. During 2004-2005, 23 crested ibises were experimentally reintroduced to an isolated basin in Qinling Mountains, where they and their offspring exhibited breeding variation never observed in wild population in the following 9 breeding seasons. Crested ibis has been considered a monogamous species, and breeding pair is solitary and territorial. However, 3.4% of breeding females exhibited polyandry and 43.1% of nests were observed colonial in single tree in the reintroduced population, probably due to male-biased sex ratio and better nesting conditions. First nest failure in reintroduced population occurred much earlier than that in wild, which resulted in significantly higher probability of re-nesting. The phenotypic plasticity in crested ibis may play important role in future reintroduction of this critically endangered species under a changing environment.