Habitat suitability models based on data of known ranges are often extrapolated to other ranges to assess suitability across large scales. However, this method often misses spatial variation of habitat selection. To consider this variation, habitat suitability should be evaluated separately in distribution ranges partitioned by environmental conditions.

We focused on Grey-faced Buzzards. Our previous study in Kyushu showed that buzzards prefer paddy-forest landscapes in regions with early rice-transplanting periods (April) and grassland-forest landscapes in regions with late rice-transplanting periods (June). We hypothesized that this spatial variation was caused by different prey abundances caused by the contrasting agricultural schedules. Here, we examined buzzard diet and prey distributions in both early and late transplanting regions in Kyushu.

We found that frogs were more abundant in the early transplanting region due to the presence of early flooded paddies. Concurrently we found that buzzards forages on frogs in the early transplanting regions, in contrast, preyed on orthopterans instead of frogs in the late transplanting regions.

This study showed that the variation of habitat selection was caused by different prey abundances resulting from different agricultural schedules. This suggests that habitat suitability for buzzards should be evaluated in each distribution range partitioned by rice-transplanting periods.