A national-scale evaluation of breeding habitat factors required for golden eagle conservation in Japan

Abstract

The golden eagle (Aquila chrysaetos) is endangered in Japan due to declines in its population size and breeding success rate. To develop conservation measures, we conducted a nationwide evaluation of factors related to golden eagle breeding habitats. We compared thirty-six 1×1-km grids containing current or abandoned golden eagle nests nationwide based on avian expert knowledge and the literature. For quantitative analysis, we used a geographic information system to establish six habitat indices representing data on the feeding and nesting environments and human disturbance around the 36 grids. Then, we constructed generalised linear mixed models, setting breeding after 2010 (yes or no) as an objective variable, the six habitat indices as explanatory variables and geology as a random effect. The results show that current golden eagle breeding habitats were positively associated with larger natural deciduous broadleaf forest areas, higher terrain slopes and longer distances from main roads, and negatively correlated with forestry activity. Natural deciduous broadleaf forest and rugged topography were found to be particularly important for the continued breeding of golden eagles. Therefore, it is important to focus on conserving these landscape elements and to investigate measures to control human disturbances such as land development and breeding interference in these areas.