Animals must strike a balance between anti-predation behavior and other essential behaviors, such as foraging. Within the same species, strategies may vary on individuals' risk-taking preferences, and in this process the environment is a determinant, in addition to predator regime. The Crested Ibis (Nipponia nippon) exhibits such tendency. This is an endangered species, once inhabiting exclusively in China's Qinling Mountain. This used to be the sole remaining wild population. However, over recent decades, this population has expanded. A portion has relocated to breed in the lower plain area, which is characterized by elevated level of human activities and landscape complexity. We used flight initiation distance (FID) as an indicator of the ibises' risk-taking preference, particularly their response to human proximity. Additionally, we examined the environmental factors influencing their foraging site selection, including altitude, terrain openness, human activity intensity and human construction. Our findings revealed a significantly shorter FID among individuals relocating to plain habitats, indicating a higher tolerance of human proximity. The results showed that FID decreased with distance to the nearest human settlement. Another finding is that FID was independent of instant human activity intensity and environmental factors (altitude and terrain openness). These different may arise from various combinations of human activity, predation risk, and food abundance within the two habitats. These results provide insights into the in situ conservation of the threatened species within the context of global urbanization.

The concept of foraging niche provides an insight into habitat use and dietary information of animals. Knowing intraspecific variation in foraging niche and trophic level is critical to the understanding of the species response to environmental changes during the process of range expansion, as well as the habitat management for conservation of threatened species. Using stable isotopic values of eggshell membranes (δ¹³C and δ¹⁵N), we examined whether there are differences in habitat use, trophic level, foraging niche width between the new and old breeding habitats (plains vs. mountains) of wild Crested Ibis (Nipponia nippon) in the early breeding season. Crested Ibis exhibited high variability in both δ¹³C and δ¹⁵N values, δ¹³C and δ¹⁵N varied as a function of habitat types. Birds breeding in plains had significantly higher δ¹³C but lower δ¹⁵N values compared to the birds breeding in mountains. Higher δ¹⁵N suggested that individuals in mountains consumed a great proportion of higher trophic level prey species in the early breeding season. Moreover, the isotopic niches were distinctly different in positions and showed small overlap between the two habitat types. The niche width was wider in old habitat than in the expanded new habitat. Our results demonstrated that the wild Crested Ibis had a high intraspecific variation in habitat uses and trophic levels in the early breeding season, and they could be divided into mountain and plain groups based on their different foraging niches. The difference in δ¹⁵N and niche width revealed that high trophic level food resources might be insufficient in plains. These findings stressed the importance of protecting foraging grounds in mountains and the necessity of improving foraging grounds in plains during winter and spring. Our study highlights the feasibility of investigating intraspecific variation in foraging ecology of birds through non-invasive isotopes of eggshell membranes. Understanding foraging niche variation gives us an insight into the food resource diversity in local areas and provides important information regarding particular foraging habitats that require protection.