3.2 Potential spatial distribution

The suitability prediction map representing the three individual models and the ensemble model (Fig.5) showed that, out of the native area, northern Australia and New Guinea were more suitable for the Asian openbill. Some islands in the Philippines and Malaysia also had high suitability values, but some high latitudes in the east Asia regions, such as China, Mongolia, Japan, and the Korean Peninsula, were less suitable.
All four maps showed that the lower latitudes were more suitable. However, we still found some records in new distribution areas with less suitable values, indicating that the Asian openbill can exist in low-suitability areas. Furthermore, three individual model results showed that there may have been more potential area in the east, northeast, and north of China. Based on the PROC evaluation, we found that the AUC ratio value of the RF model was significantly higher than other models, so it was chosen for probability analysis (Fig.6).
The occurrence probabilities for the two new distribution populations, original native populations, and random populations were extracted from the RF model for comparison. Although values of the two new distribution populations (China, Mean ± SD = 0.39 ± 0.07, Malay Peninsula, Mean ± SD = 0.4 ± 0.17) were lower than for native populations (Native, Mean ± SD = 0.49 ± 0.20), they were much higher than the expected probability (Random, Mean ± SD = 0.09 ± 0.12)(Fig.7). Based on the above suitability results, there is still a great potential for the stork to spread in both directions in China and the Malay Peninsula.