報告書番号

U03007

タイトル（和文）

イヌワシを頂点とする生態系の解明 -－秋田駒ケ岳におけるイヌワシの行動圏と狩場の植生－-

タイトル（英文）

Study on the ecosystem sustaining a pair of Golden Eagles－Vegetation of the hunting sites and the home range of a pair of Golden Eagles on Mt. Akita-Komagatake－

概要 （図表や脚注は「報告書全文」に掲載しております）

イヌワシ行動圏において植物群落の現地調査と植生図の作成を行い、GISを用いて植生分布やイヌワシ狩場としての植物群落の選好性の解析を行った。行動圏の植物群落は、森林、低木林、草原を含む40の群落に区分された。ブナ自然林、スギ植林などの主要森林群落の面積は、全行動圏の約6割を占めていた。草原、低木林、伐採跡地などの高木林以外の植物群落が占める面積は、それぞれ行動圏の5%以下であった。巣内育雛期と非繁殖期では植物群落の面積比に顕著な差が認められなかった。イブレフの選択係数による解析の結果、巣内育雛期で400ｍ以上の地域を、全期間を通じて自然草原、伐採跡地、コナラ・ミズナラ林などを狩場として選好する傾向にあった。カラマツ植林、牧草地、畑地雑草群落の選好性は季節的に変化した。本研究により、選択係数を用いた解析によって、イヌワシの生息環境としての植物群落の重要性を評価することができた。

概要 （英文）

Vegetation is an important factor for habitat condition of Golden Eagles, but it has not been evaluated from a viewpoint of behavior of Golden Eagles such as hunting. In this study, we conducted vegetation survey and analyzed vegetation distribution in the home range, and the hunting preference on plant communities was clarified using geographical information system (GIS). In the study area, forty plant communities were classified based on the phytosociological tabular comparison. Total area of main forest communities such as natural beech forest and Japanese cedar plantation occupied more than 60% of the home range. Non-forested communities such as grassland, scrub, and cut over area occupied less than 5% of the home range. Percentages of area occupied by each plant community in the home range were not different between the breeding and non-breeding season. To reveal the vegetation preference of Golden Eagles for hunting, we calculated Ivlev’s electivity index from the data of hunting sites and areas of plant communities. Natural grassland, cut over area, and secondary oak forest were positively selected in the breeding and non-breeding season. Hunting preferences on Japanese larch plantation, pasture land, and farm land differed between the two seasons. Electivity index is effective to analyze plant communities from a viewpoint of habitat conditions for Golden Eagles. Different preference may reflect food availability and food supply in plant communities. To elucidate the ecosystem sustaining Golden Eagles, further study about canopy phenology and food resource in plant communities will be needed.

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