Distribution Modelling and Habitat Use of the Eastern Great Bustard (Otis tarda dybowskii) in Eastern Mongolia

The Great Bustard (Otis tarda Linnaeus, 1758) is a globally endangered species listed as “Threatened” in the IUCN assessment. Its eastern sub-species, O. tarda dybowskii Taczanowski, 1874 occurs in Asia. Mongolia, particularly eastern part of the country is an essential place for the breeding population of the Eastern Great Bustard in East Asia. The habitat uses and assessment of the bustard in the eastern Mongolia is conducted to identify the priority breeding distribution areas to plan the further detailed management of the species in the large eastern rangeland. In modeling of the important breeding habitats for the bustard in this region, four models (GLM, GAM, GBM, RF) were used to map the breeding habitats using transmitter data during the breeding period, observation points, and BIOMOD2. Two validation methods, ROC/AUC and TSS, were used to test the optimality of these four models. Among the four selected models, the RF model is considered the best model for the habitat of the bustard population since the values of the RF model were equal to one, while the ROC and TSS values of the GAM, GBM, and GLM models were 0.8–0.88. The parameters such as the angle of view of the slope and the amount of solar radiation did not significantly affect the model results. The average monthly temperature was 15-17°C, and rainfall was 50-70 mm; therefore, there was a high probability of the bustards in rangelands near the rivers, lakes and ponds. In this modelling, 3.27% of the total 286,871.41 km2 areas analysed in the eastern Mongolian region as a suitable habitat for the bustards. The rangeland habitat is used more frequently (99.47%), and other habitats, such as water bodies, trees, and crops, were used less frequently. However, we assume that the bustard population in this region could be under heavy threats from large number of livestock and human disturbance along the river valleys, because overgrazing in the rangelands near the river valleys in Mongolia, and its biodiversity loss has been previously documented.