Changes in the Habitat Preference of Crested Ibis (Nipponia nippon) during a Period of Rapid Population Increase

The number of breeding pairs of crested ibis (Nipponia nippon) in Hanzhong, China has recovered remarkably from 2 to 511 from 1981 to 2019. Although the crested ibis has been closely monitored, the habitat preference of the bird has not been well studied despite the extensive increase in abundance. We used nest site data from the past 39 years and 30 environmental variables to develop species distribution models for each year. We applied random forest to select important environmental variables, and used logistic regressions to quantify the changes in habitat preferences in 39 years, taking into account the effects of interaction and quadratic terms. We found that six variables had strong impacts on nest site selection. The interaction term of rice paddies and waterbodies, and the quadratic term of precipitation of the wettest quarter of the year were the most important correlates of nest presence. Human impact at nest sites changed from low to high as birds increased their use of ancestral habitats with abundant rice paddies. We concluded that during the population recovery, the crested ibises retained their dependence on wetlands, yet moved from remote areas to populated rural regions where food resources had recovered due to the ban of pesticide use.

Establishment of Gut Microbiome During Early Life and Its Relationship With Growth in Endangered Crested Ibis (Nipponia nippon)

Gut microbiota during early life could influence host fitness in vertebrates. Studies on how gut microbiota colonize the gut in birds using frequent sampling during early developmental stages and how shifts in microbiota diversity influence host growth are lacking. Here, we examine the microbiome profiles of 151 fecal samples from 14 young crested ibis (Nipponia nippon), an endangered bird species, collected longitudinally across 13 time points during the early stages of development and investigated their correlation with host growth. Gut diversity showed a non-linear change during development, which involved multiple colonization and extinction events, mainly associated with Proteobacteria and Firmicutes. Gut microbiota in young crested ibis became more similar with increasing age. In addition, gut microbiota exhibited a strong temporal structure and two specific developmental stages; the beginning of the latter stage coincided with the introduction of fresh loach, with a considerable increase in the relative abundance of Fusobacteria and several Firmicutes, which may be involved in lipid metabolism. Crested ibis chick growth rate was negatively correlated with gut microbiota diversity and negatively associated with the abundance of Halomonadaceae, Streptococci, Corynebacteriaceae, and Dietziaceae. Our findings highlight the importance of frequent sampling when studying microbiome development during early stages of development of vertebrates. The role of microbial diversity in host growth during the early stages of development of birds warrants further investigations.

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

Summary Reintroductions 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.