No.127 研究課題 / Project
多摩川流域のオオタカの生息状況の実態調査とその保護策に関する調査・研究Status survey and study on protection measures for Northern Goshawk in Tama River basin| 一般研究 General Research |
No.127 |
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| 代表研究者 Principal Investigator |
尾崎 洋 hirosi ozaki |
| 所属（採択当時） Affiliation |
東京オオタカ保護連絡会会員 Member, Tokyo Otaka Protection Liaison Committee |
| 研究内容要約 Research Summary |
オオタカが住む丘陵部は、コナラを主な樹種とする雑木林、スギ・ヒノキの植林、谷戸田からなる里山であり、かつては林業、シイタケ栽培、炭焼き、水田耕作等が行われてきた。特にシイタケ栽培のため定期的な雑木林の伐採更新は、様々な生育段階の雑木林の多様性が維持され、キジ、コジュケイ、キジバト、カケスなど野島やノウサギ、リス、ネズミ類などの哺乳類を含む良好な狩場を出現させ、オオタカの繁殖率を向上させた。またオオタカの捕食圧により生態系の健全なバランスが維持され、里山経営にも寄与する形でオオタカとヒトとの共存が可能であった。 西多摩地域は、丘陵部を中心に里山生態系がまだ残されている地域である。先に述べたオオタカ営巣地の特性は、よく管理された里山の特性でもある。我々が実施したオオタカの定点観察による行動調査や食痕等の踏査調査、主な餌である鳥類調査の結果も同様にオオタカの生活様式が里山の特性に良く適応していることを実証するものであった。 現在オオタカの繁殖率が低下し絶滅の危険が増大しつつあるのは、里山が放置され、里山生態系が崩壊しつつあることが重要な一困と考えられる。したがって、オオタカを保護するためにはこの里山生態系を回復させ、維持・管理していくことが必要である。 Accipiter gentiles [northern goshawk] lives in village forests composed of the brush of Quercus serrata [white oak], afforestation areas of Cryptomeria japonica [Japanese cedar] and Chamaecyparis obtusa [Japanese cypress], and village forests with hilly paddy fields. Some industries once flourished in these areas: forest industry, shiitake mushroom cultivation, charcoal making and paddy cultivation. Reforestation and deforestation was regularly carried out for shiitake mushroom cultivation. It contributed to the formation of brush diversity with trees in various development stages. As a result, the area was full of wild birds (including pheasant, bamboo partridge, turtledove and jay) and mammals (including hare, squirrel and mouse). Such environment served as a favorable hunting area for northern goshawks, allowing their propagation. In addition, the predator pressure by the northern goshawks maintained a well-balanced ecosystem, which contributed to the management of village forest industries, also. In that respect, people lived in harmony with northern goshawks. The village forest ecosystem remains in the Nishi Tama Region, particularly in hilly areas. Nesting areas of northern goshawks are an indicator of well-managed village forests. We assessed the behavior of northern goshawks at specific observation sites, conducted field surveys to search for remains, and investigated the bird population ? the main prey of northern goshawks. The results from these studies also suggested that village forests are preferable for northern goshawks. Nowadays, village forests are poorly managed, and therefore village forest-based ecosystems are being destroyed. This fact can explain why northern goshawks are now losing their reproductive ability and are on the verge of extinction. Therefore, it is necessary to restore and manage village forest-based ecosystems. |
| 共同研究者 Collaborators |
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| 研究全文 Full Text |
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