Predicting Future Range Expansions of Blakiston’s Fish Owl Subject to Conservation Efforts

Abstract

The population of the endangered raptor species, Blakiston's fish owl Bubo blakistoni blakistoni, has been recovering recently due to conservation activities. The next conservation target is to expand their distribution, which is concentrated in eastern Hokkaido, Japan. In this study, we first built a static distribution model of the fish owl for the region in which it has stable populations. Using the habitat suitability map produced by the model, we projected the future range expansions of the owl using dynamic distribution modeling under scenarios with varied conservation activities and land-use changes. The static distribution model suggested that regions with substantial natural riparian forests and river length provided suitable owl habitats. It also indicated that maintenance and restoration of riparian forests would be important for owl conservation. Future projections of owl ranges indicated that an increase in breeding success would greatly contribute to range expansion. Additionally, the model results suggested that dispersal from the easternmost population (Konsen) was restricted due to the predominance of unsuitable surrounding areas and that existing populations are likely to expand their ranges into the currently unoccupied area in central Hokkaido (Yubari Mountains). However, there were large unexplained variations in the static distribution model and large uncertainties in the projections of future range expansions, suggesting that conservation activities should be planned flexibly and follow the actual range expansion processes of Blakiston's fish owl.