Survival rates and reproductive ecology of a reintroduced population of the Asian Crested Ibis Nipponia nippon in Shaanxi Qianhu National Wetland Park, China

Abstract

SummaryReintroductions aim to re-establish a viable population within the indigenous range of living organisms, especially of threatened species. The population of the Asian Crested Ibis Nipponia nippon, a well-known ‘Endangered’ bird species, has increased over 100 times since wild populations were rediscovered in 1981, and several reintroduction projects were subsequently carried out in its former range. An experimental release of the Asian Crested Ibis was conducted in Qianhu National Wetland Park located in the southern part of the Loess Plateau, China. It is vitally important to monitor released birds (at least their survival and breeding), to inform subsequent releases in other suitable sites. During extensive post-release monitoring, data on capture-recapture and reproductive status were obtained using banding, radiotelemetry, and field observations. Using the Cormack-Jolly-Seber (C-J-S) model, the average annual survival rates were estimated to be 0.569 (95% CI: 0.353–0.762) for released individuals and 0.643 (95% CI: 0.038–0.987) for all individuals. From 2014 to 2018, a total of 14 breeding pairs produced 28 eggs and 10 fledglings with successful reproduction of the second generation. The mean clutch size was 2.07 ± 0.25 (n = 29), and the breeding success was 34.5%. Predation and poor habitat quality have been shown to be the main factors affecting the reintroduced population at establishment stage. Some management suggestions at the metapopulation and ecosystem levels, including further release, predator control and habitat improvement, have been proposed.