Fig. 3.(a)The percent contribution of the environment variables in current distribution of birds(b) The comparison of percentage contribution of 5 essential variables in different scenarios
This result indicated the 5 factors were of great significance for the current distribution of birds. In the future scenarios, the most important variable is still\(t_{\min}\), of which the percent contribution is 23.89% in RCP2.6 and 31.17% in RCP8.5(Fig.3b). It can be seen that the temperature is the main environmental factor that affects the potential distribution area of the migratory birds. The combined percent contribution of all climate variables are 53.59% in RCP2.6 and 59.13%in RCP8.5, and climate change still has a great influence on the distribution of migratory birds in future.
The appropriate living conditions of the migratory birds can be viewed through the single-factor response curves of 5 most important environmental variables (Fig.S2). From the 5 most important variables, we can know that birds prefer to live in the plains with a warm climate and abundant water resources (Ma et al., 2019; Yong et al., 2018). Flat terrain means flying distance to search food is shorter and consuming energy is less. The warm climate and rich water resources mean food resources are rich for the migratory birds (Myers et al., 2000). When the temperature changes, the suitable area of the migratory birds shifts. The transferred area may overlap with the human living space, which will cause the living space for migratory birds to be compressed(Fournier et al., 2019).

The distribution of endangered species

The distribution of endangered species is always used in the division of protected areas (Lehikoinen et al., 2019; Manish & Pandit, 2019; Runge et al., 2015; Sang et al., 2011; Shen et al., 2015; Xu et al., 2017), which identifies areas that need priority protection and has positive implications for planning and constructing of protected areas. 23 species of different endangered level on the IUCN red list were used in our model to comprehend the current potential distribution and the future habitat. The comparison between the current situation and future distributions of species is showed in Fig.4.