山 階 鳥 研 報(J. Yamashina Inst. Ornithol),34:228-231,2002

The Drastic Decline of Breeding Population on Brown cristatus superciliosus at Nobeyama Plateau in Central

Sadao Imanishi*

Key words: Lanius cristatus superciliosus, Drastic decline of breeding population, Forest fires, , Wintering areas. キ ー ワ ー ド:ア カ モ ズ(Lanius cristatus superciliosus),繁 殖 個 体 群 の 激 減,森 林 火 災,イ ン ドネ シ ア,越 冬 地.

The decline of numbers of summer resident was recently reported in Japan (Higuchi 1999). The of Brown Shrike Lanius cristatus superciliosus, one of the summer residents, breeds from central Honshu to Hokkaido in Japan (CCJB 2000). This subspecies also decreased in Hokkaido over 20 years (Haas & Ogawa 1995) and at some areas in Honshu (Morishita & Higuchi 1999). I report the drastic decline on the numbers of Brown Shrike documented in the course of my studies of the relationship between Cuculus canorus and their hosts, the sex difference of adult Brown , and the timing of post-juvenile molt of Brown Shrikes. The study was performed within an approximately 15km2 study area in Nobeyama plateau at southeast foot of Mts. Yatsugatake, in east-central Nagano Prefecture, central Japan (35° 57'N, 138° 28'E, ca. 1,350 m elevation, see Imanishi 2002). I found the nests of Brown Shrike or pairs with fledglings during breeding season from 1992 to 2002. The number of breeding birds was calculated by doubling the number of pairs, because this is basically monogamous (Haneda & Takahashi 1967). There was one interspecific pair with a female Bull-headed Shrike L. bucephalus bucephalus from 1992 to 1994, and with a female Shrike L. tigrinus at 2002 (Imanishi unpubl. data), so in these four years one , a male Brown Shrike, was added. The number of breeding birds was largest in 1993. From 1994-1997 the population size remained between 50 and 60 birds, but drastically decreased in 1998 to 20 birds and after that to 2002 has kept stable at a low level under 10 birds (Fig. 1). Takagi (2002) suggested that the decline of this subspecies in his study area in Hokkaido was resulted from the loss and modification of , but the drastic decline of 1998 and the continued reduction in my study area cannot be accounted for by the change in . The breeding habitats of Brown Shrikes in my study area are forest edge adjacent to hayfield, shrubs in wasteland with grass, or open woods. The land usage in Nobeyama plateau is mostly vegetable fields and hayfields. During the course of this

Received 21 August 2002, Revised 24 Sept. 2002, 2nd Revision 8 Oct. 2002, Accepted 10 Oct. 2002. * Department of Human Science, Faculty of Humanities, Wako University, Machida, , 195-0071 Japan. Present address: Yamashina Institute for Ornithology, Konoyama, Chiba 270-1145, Japan. E-mail: [email protected]. ne. jp

228 The Drastic Decline of Breeding Population on Brown Shrike L. c. superciliosus 229

Fig. 1. Change of breeding population of Brown Shrike from 1992 to 2002 at study area in Nobeyama plateau, central Japan. An arrow shows the start of the fires in Indonesia. study, some hayfields and wastelands where shrikes used as foraging or nesting areas were converted to vegetable fields or residential developments. In other fields, shrubs that provided important nesting or perching sites were partly cleared. The quality of habitat for Brown Shrikes in study area appears to have declined gradually during this time period, but these changes cannot account for the drastic decline of 1998 and the subsequent reduction, because the change of habitats was not drastic from 1997 to 1998. The large and rapid decline in shrike numbers without comparable changes in conditions on the breeding grounds implicates events on the wintering grounds. This subspecies winters mainly in two areas: one is the southern coast of through and the other is Sumatra I., Java I., Sumbawa I., Sumba I. and Flores I. in Indonesia (Lefranc & Worfolk 1997). The habitats of Brown Shrike, including this subspecies, in wintering areas are open woods, gardens, scrubs, wastelands and grasslands (Medway 1970, Severinghaus & Liang 1995, Harris & Franklin 2000). In Indonesia unusually large forest fires started in the summer of 1997, and the fires burned extensive areas on the above islands, as well as Kalimantan I. and Celebes I. and others from August to October on 1997 (Simons 1998), and still continued to burn peatlands through 2002 (Hanawa pers. comm.). The areas of the fires in 1997/98 was about 9.5 million hectares, of which 51% was not forests but grasses, agricultural wastes, scrubs, and non-woody swamp vegetation (Schweithelm 1999, Rowell & Moore 2000). It is likely that these long-term and extensive fires might have reduced usable wintering habitat for shrikes. Although the wintering areas of Brown Shrikes breeding at Nobeyama and other areas in Japan have been unknown yet, the drastic decline of Brown Shrikes in my study areas in 1998 may be a result of Indonesia' fires. The fact that the decline occurred in the breeding season immediately following the season of Indonesian fires (see Fig. 1) provides strong circumstantial evidence that loss of wintering habitat may be a problem. Haas & Ogawa (1995) have suggested that the decline of populations of this subspecies in Hokkaido might result from the loss and degradation of habitat in Indonesia. My finding may support their suggestion. 230 Sadao Imanishi

I am grateful to Mr. T. Yoshino and Mr. Y. Yoshida for getting me information of nests of shrikes. I thank Ms. H. Arai, Mr. S. Hanawa, Mr. T. Hiraoka, Mr. K. Ozaki and Ms. M. Turumi for their information of forest fires in Indonesia and Dr. M. Takagi and Dr. S. Yamagishi for their useful comments on my manuscript. I also greatly thank Dr. C. A. Haas for her kindly comments and improving my English on my manuscript.

References CCJB (The Committee for Check-List of Japanese Birds) (ed.) 2000. Check-List of Japanese Birds. Sixth Revised Edition. The Ornithological Society of Japan, Hokkaido. 345 pp. Haas, C. A. & Ogawa, I. 1995. Population trends of Bull-headed and Brown Shrikes in Hokkaido, Japan. In Shrikes (Laniidae) of the World: Biology and Conservatio (eds. R. Yosef & F. E. Lohrer). Proceedings of the Western Foundation of Vertebrate Zoology 6: 72-75. Haneda, K. & Takahashi, Y. 1967. Life history of the Japanese Red-tailed Shrike (Lanius cristatus super- ciliosus). I. Breeding Season. Japanese Journal of Ecology 18: 47-56. (in Japanese with English Summary). Harris, T. & Franklin, K. 2000. Shrikes and Bush-Shrikes. Princeton University Press, New Jersey. 392 pp. Higuchi, H. (ed.) 1999. Research Report on the Population Decline of Tropical Migratory Birds. University of Tokyo Research Group of Migratory Birds, Tokyo. 110 pp. (in Japanese). Imanishi, S. 2002. The home range and flock size of the Azure-winged Magpie Cyanopica cyana during the non-breeding season in Nagano Prefecture. Japanese Journal of Ornithology 51: 62-73. (in Japanese with English abstract). Ishigaki, K. 1966. The interspecific territoriality between the shrikes, Lanius Bucephalus and L. cristatus, in their cohabiting area. Japanese Journal of Ecology 16: 87-93. (in Japanese with English synopsis). Lefranc, N. & Worfolk, T. 1997. Shrikes-A Guide to the Shrikes of the World. Pica Press, Sussex. Medway, L. 1970. A ringing study of the migratory Brown Shrike in west . Ibis 112: 184-198. Morishita, E. & Higuchi, H. 1999. Population decline of tropical migratory birds based on birdwatching record. In Research Report on the Population Decline of Tropical Migratory Birds. (ed. H. Higuchi), pp. 19-43. University of Tokyo Research Group of Migratory Birds, Tokyo. (in Japanese). Rowell, A. & Moore, P. F. 2000. Global Review of Forest Fires. WWF and IUCN, (http://panda.org/ forests4life/fires/) Schweithelm, J. 1999. The Fire This Time an Overviewof Indonesia's Forest Fires in 1997/98. WWF Indonesia, Jakarta. 44 pp. Severinghaus, L. L. & Liang, C. T. 1995. Food and foraging behavior of the Brown Shrike Lanius cristatus in Taiwan. In Shrikes (Laniidae) of the World: Biology and Conservation (eds. R. Yosef, & F. E. Lohrer). Proceedings of the Western Foundation of Vertebrate Zoology 6: 194-199. Simons, L. M. 1998. Indonesia's plague of fire. National Geographic (8): 100-119. Takagi, M. 2002. Philopatry and habitat selection in Bull-headed and Brown Shrikes. Journal of Field Ornithology (in press). Takagi, M. & Ogawa, I. 1995. Comparative studies on nest sites and diet of Lanius bucephaius and L. cristatus in northern Japan. In Shrikes (Laniidae) of the World: Biology and Conservation (eds. R. Yosef & F. E. Lohrer). Proceedings of the Western Foundation of Vertebrate Zoology 6: 200-203. The Drastic Decline of Breeding Population on Brown Shrike L. c. superciliosus 231

長野県野辺山高原におけるアカモズLanius cristatus superciliosusの 繁殖個体数の激減

日本 では最近夏鳥 の数 が減少 し,こ の夏鳥 の一種 のアカモズの一亜種Lanius cristatus super- ciliosus も北海道 やその他 の地域 で減少 している。長野県 の野辺 山高原 の調査地 で繁殖す る この 亜種 の1992年 か ら2002年 の11年 間の繁殖個体数 の変化 のデータを得 た。 繁殖個体数 は1993 年 に最 も多 く,そ の後1997年 までは50～60羽 であ った。 しか し,1998年 にはそれまでの約 1/3の20羽 に激減 し,そ の翌年 か ら2002年 まで は10羽 以下 に減少 した。調査地 でのアカモズ の生息環境 は徐 々に悪 くな ってい るが,1997年 以降特 に激変 していない。アカモズの この亜種 の主 な越冬地 の1つ はイ ン ドネ シアであ る。イ ン ドネ シアで は人為的 な火入 れが1997年8月 よ り大火災 にな り,こ の火災 は1998年 には一時下火 になったが,そ の後 も火災 は続 いて いる。 この大火災 の発生 時期 とアカモズの激 減の時期が一致 して いるため,ア カモズの1998年 の激 減 の原因 は越冬地 であ るイ ン ドネ シアの大火 災であ ると考 え られ,そ の後 の減少 もこの火災 の 影響 によ ると考 え られ る。

今西 貞夫:和 光大学 人間関係学部.〒195-0071東 京都町 田市金井町2160. 現所属:山 階鳥類研究所.〒270-1145千 葉県我孫子市高野 山115.