報告書番号

U01021

タイトル（和文）

イヌワシを頂点とする生態系の解明 --イヌワシの餌資源利用の特徴--

タイトル（英文）

Study on the ecosystem sustaining a pair of Golden Eagles-Food resource use on Golden Eagles-

概要 （図表や脚注は「報告書全文」に掲載しております）

イヌワシと餌動物との関係を定量的に解明する研究の一環として、イヌワシの餌資源利用を明らかにするために既存の文献を整理した。また、当所の調査地である秋田駒ヶ岳で予備的な現地調査を行い、この結果をまじえてイヌワシの育雛期の餌資源利用に関する解析を行った。この結果、1)イヌワシの育雛期の主要な餌動物群は、世界的にみると哺乳類と鳥類で、国や地域によって餌種やその構成比は異なること、2)日本では、育雛期の餌種ではノウサギ、ヤマドリ、アオダイショウの利用頻度が高く、他国に比べヘビ類の利用が多いこと、3)秋田駒ヶ岳の育雛期の餌では他地域に比べてノウサギの占有率が高く、育雛期後半の巣への餌搬入頻度は低い傾向にあること、4)イヌワシの餌量に関する報告は少なく、秋田駒ヶ岳で育雛期の餌量を算出するために、巣内に搬入される餌種やサイズなどを連続的な画像記録を用いて明らかにする必要のあること、などが示された。

概要 （英文）

To clarify food resource use of Golden Eagles Aquila chrysaetos, previous reports were reviewed. In addition, to understand the food resource use by a breeding pair on the foot of Mt. Akita-Komagatake, an observation was carried out at the nest site during the later period of a nestling season in 2000.Major foods of Golden Eagles in the world were mammals and birds, however, prey species or their occupancies differed among pairs or nesting areas, or countries.The primary prey of Golden Eagles in Japan during nestling seasons was Japanese hare Lepus brachryurus, and was followed by Copper Pheasant Syrmaticus soemmerringi and one species of snakes, Elaphe climacophora. It was a character in Japan that snakes were one of major prey species. Although the information on foods of Golden Eagles during non-nestling seasons was very scarce in Japan, they may use different food resources from breeding seasons.The primary prey during nestling seasons for the breeding pair on Mt. Akita-Komagatake was Japanese hare, which occupied 73.7% in all preys identified. This occupancy was higher than the average of other nesting sites in Japan. The frequency which parent birds carried foods in the nest on Mt. Akita-Komagatake was lower than that in other nesting sites, especially in the later period during nestling season. The food availability might be low during this period on Mt. Akita-Komagatake.There were few reports on food consumption for Golden Eagles in Japan. They were estimated to be about 220-230 g / day for an adult eagle and about 300 g / day for a nestling. Biomass of prey brought to a nest was about 1,000 g / day according to previous reports, however, these reports did not insert the weight for prey species every body size. To calculate food consumption of nestlings at the nest site on Mt. Akita-Komagatake, it is needed to clarify prey species and their sizes carried in the nest.

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