山 階 鳥 研 報(J.Yamashina Inst.Ornithol.),33:107-141,2002

Status of Seabirds Breeding in Hokkaido

Yuichi Osa* and Yutaka Watanuki**

Abstract. The historic and present status of seabirds in Hokkaido is summarized, based on published and unpublished data. At least 12 species breed in Hokkaido. The breeding pairs of seabirds in recent years in Hokkaido are estimated as follows: Common Murre (Uria aalge) <10; Tufted Puffin (Lunda cirrhata) 15; Spectacled Guillemot (Cepphus carbo) 100; Ancient Murrelet (Synthliboramphus antiquus) <20; Rhinoceros Auklet (Cerorhinca monocerata) 300,000; Slaty-backed Gull (Larus schistisagus) 10,000; Black-tailed Gull (Larus crassirostris) 30,000; Red-faced Cormorant (Phalacrocorax urile) 25; Japanese Cormorant (Phalacrocorax capillatus) 3,000; Pelagic Cormorant (Phalacroc- orax pelagicus) 10; Streaked Shearwater (Calonectris leucomelas) 120; Leach's Storm- petrel (Oceanodroma leucorhoa) 900,000. The present status of the Long-billed Murrelet (Brachyramphus perdix) is unclear. The colony size of Common Murre shrank with annual decreasing rate of 12.2% (1938-80)～26.6% (1981-94) on Teuri Island. It has decreased 24.8% annually, and it has not been observed on Moyururi Island since 1985.

The Tufted Puffin and Spectacled Guillemot decreased 9～15% annually during the last 30

years. The Slaty-backed Gull increased 11.0% annually (1963-95) on Teuri Island, and 8.5% annually (1972-93) on Yururi Island. Black-tailed Gull increased by 5% annually

(1987-2000) on Rishiri Island, but decreased on Teuri Island during the 1990's. The Japanese Cormorants increased by 5～9% annually on Teuri and Yururi Islands. Its number increased at annual rate of 6.4% during 1959-86, but decreased at annual rate of 10.4% during 1987-96 on Moyururi Island. At 12 of the 14 surveyed colonies predation by gulls and/or crows were reported, and disturbances caused by introduced rats and cats was reported at five colonies. Although most of the colonies are legally protected, few conservation programs have been effectively conducted. Seabird mortality by fishing nets was reported around six colonies, but protective measure for seabirds has not been taken. We here propose, therefore, non-fishing sea areas for seabird protection around such breeding islands. Key words: Colony size, Conservation, Disturbance, Seabird in Hokkaido. キ ー ワ ー ド:繁 殖 地 サ イ ズ,保 全,攪 乱,北 海 道 の 海 鳥 類.

Introduction

Hokkaido lies between 41°30'N and 45°30'N and 139°30'E and 145°50'E surrounded by Okhotsk Sea, Japan Sea, and Pacific Ocean, and has 2668km of coastline, with about 15 islands and many islets which provide breeding sites for seabirds. The marine ecosystem surrounding Hokkaido is highly productive and supports many species of

Received 23 July 2001, Revised 1 December 2001, Accepted 27 December 2001. Paper presented in a symposium held by the Japanese Seabird Group and Pacific Seabird Group (Lihue, Hawaii; February 2001). * Nature Conservation Department , Hokkaido Institute of Environmental Sciences (HISS), Kita-19 Nishi-12,Kita-ku, Sapporo, 060-0819, Japan. E-mail:osa@hokkaido-ies. go. jp

** Laboratory of Animal Ecology , Graduate School of Agriculture, Hokkaido University, Sapporo, 060- 8589, Japan.

107 108 Yuichi Osa and Yutaka Watanuki

seabirds. The Kuroshio warm and Oyashio cold currents meet along 36°-40°N on the Pacific coast, and the waters of Hokkaido and the adjacent southern Kurile Islands are rich enough to support huge breeding populations of seabirds, especially Leach's Storm- petrel (Oceanodroma leucorhoa), Rhinoceros Auklet (Cerorhinca monocerata), and the endemic Black-tailed Gull (Larus crassirostris). Watanuki et al. (1988b) summarized the status of breeding seabirds in Hokkaido before the 1990's, and suggest the decrease of breeding Common Murre (Uria aalge), Tufted Puffin (Lunda cirrhata ), Spectacled Guillemot (Cepphus carbo), and Red-faced Cormorant (Phalacrocorax urile). Thereafter, no status report has been published. The Japan Environmental Agency (JEA) categorized the Common Murre, Tufted Puffin, and Red-faced Cormorant as national endangered species in 1993, and has been running conservation projects for these three species since 1996 (Conservation Projects for Endangered Species of Seabirds in Hokkaido). As a part of this project, we summarize here the status of breeding seabirds in this area of Japan. Breeding seabirds in Hokkaido have experienced human-induced disturbances, in- cluding egging and hunting by domestic people, between the 1920's-1960's (Murata 1957, Ogi et al. 1995). Recently, predation by Slaty-backed Gulls (Larus schistisagus), Jungle Crow (Corvus macrorhynchos) and Carrion Crow (Corvus corone) on the eggs and chicks of breeding seabirds (JEA 1973, Haga 1973, Hayashida & Hashimoto 1981, Nakagawa 1981, Kondo et al. 1986, Watanuki et at. 1988b, Kondo et al. 1991a, 1991b, Kosugi 1991, Kondo 1992, Takeda et al. 1992, Fukuda et al. 1995), and disturbances by rats, cats and dogs introduced to the islands have been reported (Kuroda 1963, Kuroda 1965, JEA 1973, Kondo et al. 1986, Watanuki et al. 1988b, Fukuda et al. 1995, Miyazaki 1995, Ogi et al. 1995). The risk of entanglement in fishing equipment is believed to have increased in recent years (JEA 1973, Kondo et al. 1986, Kondo et al. 1991a, 1991b, Kondo 1995). Therefore, we also reviewed the reports documenting these disturbances to breeding seabirds, to further promote seabird conservation activities in Hokkaido.

Methods

We reviewed research reports published from 1938-2001, and categorized the census methods to: a. The researcher counted the number of all individuals or pairs in a colony; b. The researcher made local sampling counts, and estimated the entire numbers of birds of a breeding colony; c. The researcher estimated very roughly the number of individual or pairs, and d. The researcher counted the number of individuals at sea around the colony (see Appendix 1). We calculated the annual rate of the change of seabird population by regression analysis following Watanuki et al. (1988b), when consecutive data were available. These annual change rates are not accurate, because data was not always collected at regular intervals. However, these rough annual change rates are useful to follow the long term trends (Matsuda 2000). In showing the colony size by range, we selected the minimum value. We used the annual change rate to assume the change of colony size, though the proportion of non-breeders was unknown. Disturbances to seabird colonies by natural and human causes have been Status of Seabirds Breeding in Hokkaido 109 discussed (ICBP 1984). The introduction of rats, cats, dogs, horses, and rabbits caused the mortality of birds and destruction of their breeding habitats (Moor & Atkinson 1984). Commercial fishing accidentally killed many seabirds by catching them in various types of fishing gear (Ogi 1984, Jones & DeGange 1988). Other human disturbances included tourists who would approach too close to seabird nests, and rock blasting, which is conducted to help better growth of the kelp (Kondo et al. 1991a, 1991b). Slaty-backed Gulls, Jungle Crows and/or Carrion Crows killed the chicks and eggs of Black-tailed Gulls and Rhinoceros Auklets (Watanuki 1983). Climatic factor which caused higher water temperature and human factor of excessive fishing gave negative effects to the abundance of seabirds' marine food resources. The disturbances factors affecting seabird colonies can be categorized as follows: 1) Predation by introduced rats or cats; 2) Other introduced animals; 3) Harvest of eggs or adults by human for food; 4) Death caused by being caught in commercial fishing nets; 5) Other human-induced disturbances (such as sightseeing activities, aircraft noise, rock blasting to create kelp growing habitats, etc.); 6) Predation or prey-plunder by gulls or crows; 7) Other natural factors (change of prey resources, etc.)

Results 1. Status of colonies Approximately 29 colony areas are known in Hokkaido (Fig. 1), but some small colonies might have been overlooked, such as those consisting of a few gull nests, hole or inter-rock nests of alcids or storm-petrels. In Hokkaido, at least 12 species breed, which include five alcids, two gulls, three cormorants, one shearwater, and one storm-petrel (Table 1). The breeding evidence of the Long-billed Murrelet (Brachyramphus perdix) is documented in Sekine (1987), but the further investigation is under way in Shiretoko Peninsular (Fukuda 2001, Nelson et al. in press). 1) Common Murre (Uria aalge ) The Common Murre is reported to breed on Yururi Island (Nagata 1959), Moyururi Island (Abe & Matsuki 1968), Matsumae-kojima (JEA 1973), and Teuri Island (Murata 1957, JEA 1973, 1978, Watanuki et al. 1986, Watanuki et al. 1988b, Terasawa 1990, 1991, Takeda et al. 1992, Terasawa et al. 1995), but at present it breeds only on Teuri Island. The colony size on Teuri Island decreased at annual rate of 12.2% during 1938-80 and decreased at annual rate of 26.6% during 1981-94 (Table 2). In 1998, only seven breeding pairs were confirmed (Hokkaido Government 1999). On Moyururi Island, the colony size of the Common Murres decreased by 24.8% annually during 1965-83 (Table 2), and no individual has been observed since 1985. The colony sizes on Yururi Island fluctuated, showing no clear trend, and no birds have been observed there since 1985 (Kondo et al. 1986). 110 Yuichi Osa and Yutaka Watanuki

Fig. 1. Location of colony in Hokkaido. 図1北 海道内の海鳥繁殖地の位置 Colony (繁 殖 地): 1, Habomaimoshiri and Isomoshiri Is. (ハ ボ マ イ モ シ リ ・イ ソ モ シ リ 島);2, Tomoshiri and Chitomoshiri Is. (友 知 ・チ トモ シ リ島);3, Hanasaki Coast (花咲 海 岸 域);4, Konbumori and Hamamatsu Coast (昆布 盛 ・浜松海 岸域); 5, Kamojima (カ モ 島);6, Moyururi I. (モ ユ ル リ 島); 7,Yururi I.(ユ ル リ 島);8,Cape Ochiishi(落 石 岬);9,Cape Toufutsu(湯 沸 岬);10,Kiritappu-kojima(霧 多 布 ・ 小 島)11,Kenbokki I.(ケ ン ボ ッ キ 島); 12,Hamanaka Coast(浜 中 海 岸 域);13,Daikoku I.(大 黒 島);14,Kushiro Coast(釧 路 町 海 岸

域);15,Cape Erimo(襟 裳 岬);16,Muroran Coast(室 蘭 海 岸 域);17,Cape Esan(恵 山 岬);

18,Mt.Hakodate Coast(函 館 山 海 岸 域);19,Matsumae-kojima(松 前 小 島);20 , Oshima-ohoshima(渡 島 大 島);21,Okushiri I.(奥 尻 島);22,Cape Ofuyu(雄 冬 岬);23,Teuri I.(天 売 島);24,Rishiri I.(利 尻 島);25,Rebun I.(礼 文 島);26,Esashi-menashidomari(枝 幸

町 ・ 目 梨 泊);27,Esashi-gomeiwa(枝 幸 町 ・ ゴ メ 岩);28,Koshimizu Area(小 清 水 町 内 陸 域); 29,Shiretoko Pen.(知 床 半 島)

Table 1. Breeding status and the last ten years trend of colony in Hokkaido. 表1北 海 道 の 海 鳥 類 の 生 息 状 況 と最 近10年 間 に お け る動 向 Status of Seabirds Breeding in Hokkaido 111

Table 2. Annual change rate of seabirds' colony size. 表2海 鳥繁殖地のサイズの年平均増減率

2) Tufted Puffin (Lunda cirrhata) Tufted Puffins bred on Tomoshiri Island (Fujimaki 1986), Yururi Island (Haga 1973, Kondo et al. 1986), Moyururi Island (Fujimaki 1961, Abe & Matsuki 1968, Haga 1973, Kondo et al. 1986, Kondo et al. 1991b), Daikoku Island (Abe et al. 1972, Watanuki et al. 1988b, Kondo et al. 1991a, Niizuma 1995), Cape Toufutsu and Kiritappu-kojima (Kataoka & Mizuno 1999). Although one pair started to show breeding behavior at Kiritappu colony in 1996, their breeding was unsuccessful, because one mate of the pair disappeared (Kataoka & Mizuno 1999). On Moyururi Island, the colony size decreased 10.0% annually during 1960-95 (Table 2). On Yururi Island, 5-9 pairs bred every year from 1997-2000 (Ministry of the Environment, unpublished data). The Tufted Puffin is rarely observed on Daikoku Island, and there is no evidence of breeding activity (Shibuya, unpublished data). 3) Spectacled Guillemot (Cepphus carbo) Spectacled Guillemots bred on Teuri Island (Murata 1957, Kuroda 1963, JEA 1973, 1978, Thoresen 1984, Terasawa et al. 1995, Fukuda et al. 1995), Tomoshiri Island (Fujimaki 1986), Habomaimoshiri Island (Tamada et al. 1997), Yururi Island (Haga 1973, Watanuki et al. 1988b, Kondo 1995), Moyururi Island (Abe & Matsuki 1968, Haga 1973, Watanuki et al. 1988b, Kondo et al. 1991b), Cape Esan (Kuroda 1958), Matsumae- kojima (JEA 1973), Daikoku Island (Abe et al. 1972, Kondo et al. 1991a), Shiretoko Peninsular (Kuroda 1965, Nakagawa 1981, Fukuda 2001) and Kenbokki Island (Kondo et al. 1991a). Reliable information on their present breeding status was collected on 112 Yuichi Osa and Yutaka Watanuki

Teuri, Yururi and Moyururi Islands and on Shiretoko Peninsular, though the number of active nests was rarely documented, since the nests in rock crevices were rarely reached. The number of birds on Teuri and Yururi Islands decreased by 8.8% and 14.4% annually, respectively (Table 2). The trend towards decrease of its population on Moyururi Island is, however, insignificant. On Daikoku Island, the observed number decreased from 80 individuals in 1982 (Watanuki et al. 1988b), to one individual in 1996 (Nakamura et al. 1997). 4) Ancient Murrelet (Synthliboramphus antiquus) This species had been recorded as breeding on Habomaimoshiri (Watanuki et al.1988b) and Teuri Islands (Murata 1958, Kuroda 1963, Watanuki et al. 1986, Watanuki et al. 1988 b, Fukuda et al. 1995 ), though limited information on their present status is available. We were not able to make a conclusion about whether the population was increasing or decreasing. The colony size on Teuri Island was estimated to be less than 100 individuals in 1993-94 (Fukuda et al. 1995). 5) Rhinoceros Auklet (Cerorhinca monocerata) This species bred on Tomoshiri Island (Fujimaki 1986), Yururi Island (Haga 1973, Kondo et al. 1986, Watanuki et al. 1988b, Kondo et al. 1991a, Kondo 1995, Osa 1998), Moyururi Island (Fujimaki 1961, Abe & Matsuki 1968, Haga 1973, Kondo et al. 1986, Watanuki et al. 1988b, Kondo et al. 1991b, Sato 1995b, Osa 1998, Sato 1998), Matsumae- kojima (Kuroda 1965, JEA 1973, Technical Team of Wild Bird Society of Japan 1985), Daikoku Island (Watanuki et al. 1988b, Kondo et al. 1991a, Niizuma 1995, Nakamura et al. 1997, Sato 1997), Teuri Island (Murata 1957, Kuroda 1963, JEA 1973, 1978, Watanuki et al. 1986, Miyazaki 1995) and Rebun Island (Chishima unpublished data, Konno unpublished data). It is difficult to estimate the number of active nest burrows, and few estimations have been done. The number of estimated burrows on Moyururi Island increased by 14.2% annually (Table 2). Although trends regarding the size of the colonies on Teuri and Yururi Islands were not clear, the colony sizes may have increased or remained stable. 6) Slaty-backed Gull (Larus schistisagus) The Slaty-backed Gull is a popular large breeding gull that lives along coastal areas in Hokkaido. More than 1000 pairs bred on Yururi (Haga 1973, JEA 1973, Kondo et al. 1986, Watanuki et al. 1988b, Kondo 1995, Tamada et al. 1997), Moyururi (Fujimaki 1961, Abe & Matsuki 1968, Haga 1973, JEA 1973, Kondo et al. 1986, Watanuki et al. 1988b, Kondo et al. 1991b, Tamada et al. 1997, Sato 1998), Teuri (JEA 1978, Watanuki et al. 1986, Terasawa & Aotsuka 1986, Watanuki et al. 1988b, Terasawa 1991, Fukuda et al.1995) and Daikoku Islands (Abe et al. 1972, Hayashida & Hashimoto 1981, Watanuki 1986, Watanuki et al. 1988b, Kondo et al. 1991a, Niizuma 1995, Nakamura et al. 1997, Sato 1997). The number of active nests increased by 11.0% annually on Teuri Island, and by 8.5% annually on Yururi Island (Table 2). Recent data suggests that the breeding number was stable or decreasing during 1996-2000 on Teuri Island, but this trend was not clear. The colony size on Moyururi Island increased by 8.6% annually until the 1970's, and decreased by 7.0% annually since the 1980's (Table 2). However, the colony size on Daikoku Island increased 8.9% annually during 1951-96. Status of Seabirds Breeding in Hokkaido 113

7) Black-tailed Gull (Larus crassirostris) Black-tailed Gulls were known to breed on Yururi Island (Kondo et al. 1986, Watanuki et al. 1988b, Kondo et al. 1991b), Moyururi Island (Abe & Matsuki 1968, Haga 1973, Tamada et al. 1997, Sato 1998), Matsumae-kojima (Kuroda 1963, JEA 1973, Technical Team of Wild Bird Society of Japan 1985), Daikoku Island (Hayashida & Hashimoto 1981, Watanuki et al. 1988b), Shiretoko Peninsular (Fukuda 2000, 2001), Teuri Island (Murata 1957, Kuroda 1963, JEA 1973, Watanuki 1982, Watanuki et al. 1986, Watanuki et al. 1988b, Fukuda et al. 1995), Rishiri Island (Watanuki et al. 1988b, Kosugi 1991), and Okushiri Island (Hayashi unpublished data). On Teuri Island, 30,000 pairs of Black-tailed Gulls bred in the 1980's, but their breeding numbers decreased by half in the 1990's (Watanuki 1995). This species had not been breeding on Moyururi Island during 1983-95 (Kondo et al. 1986, Kondo et al. 1991b, Sato 1995b), has been breeding since 1996 (Tamada et al. 1997), and increased to 27,000 individuals in 2000 (Hokkaido Government, unpublished data). The colony size increased on Yururi Island up to 1987, but no breeders were observed there at present. On Rishiri Island, 200 new pairs have started to breed since 1987 (Kosugi 1991), and the colony size increased by 19.5% annually during 1987-2000 (Soya Subprefecture of Hokkaido Government 2001, Table 2). On Rishiri Island, 200-1,500 adult Black-tailed Gulls were culled every year from 1993 to 2000 by islanders, to lessen the suspected damage to harvested sea urchin (Strongylocentrotus intermedius) and sea weeds, and public nuisance. 8) Red-faced Cormorant (Phalacrocorax urile) This species was reported to breed intermittently on the pacific coast of the Nemuro Peninsula. The species bred on Yururi Island (Nagata 1959, Haga 1973, JEA 1973, Fujimaki et al. 1976, Fujimaki 1986, Kondo et al. 1986, Watanuki et al. 1988b, Kondo et al. 1991b), Moyururi Island (Fujimaki 1961, Abe & Matsuki 1968, Haga 1973, JEA 1973, Fujimaki et al. 1976, Kondo et al. 1986, Watanuki et al. 1988b, Kondo et al. 1991b, Kondo 1995) and Kamojima (Fujimaki et al. 1976, Ministry of the Environment, unpublished data). In 1996, two active nests were found on Kamojima near Moyururi Island, and 28 nests were observed on Kamojima and Yururi and Moyururi Islands in 2000 (Ministry of the Environment, unpublished data). On Yururi and Moyururi Islands, breeding pairs changed the nest site every year (Kondo 1995, Ministry of the Environment, unpublished data). 9) Japanese Cormorant (Phalacrocorax capillatus) This species bred on the pacific coast between Nemuro City and Hamanaka Town (Kondo et al. 1991a, Nakamura et al. 1997), Yururi Island (Haga 1973, Fujimaki et al. 1976, Fujimaki 1986, Kondo et al. 1986, Watanuki et al. 1988b, Kondo 1995, Tamada et al. 1997), Moyururi Island (Fujimaki 1961, Abe & Matsuki 1968, Haga 1973, Fujimaki et al. 1976, Kondo et al. 1986, Watanuki et al. 1988b, Kondo et al. 1991b, Kondo 1995, Sato 1995b, Tamada et al. 1997, Sato 1998), Rebun Island (Chishima unpublished data, Konno unpublished data), the Shiretoko Peninsula (Nakagawa 1981, Fujimaki 1985, Nakagawa 1985, Watanuki et al. 1988b, Fukuda 2001), and Teuri Island (Murata 1957, Kuroda 1963, JEA 1978, Watanuki et al. 1988b, Fukuda et al. 1995). A small colony (1-100 nests) was found on Tomoshiri Island (Tamada et al. 1997), Hamamatsu Coast (Kondo 114 Yuichi Osa and Yutaka Watanuki et al. 1991a), Cape Ochiishi (Tamada et al.1997), Kushiro Coast (Nakamura et al. 1997), Cape Ofuyu (Shimada 1984) and Cape Esan (Kuroda 1958, 1965). The number of active nests increased by 8.9% annually on Teuri Island and by 4.9% annually on Yururi Island (Table 2). On Moyururi Island, the number of nests increased by 6.4% annually during 1959-86, and has decreased by 10.4% since 1987 (Table 2). The number of nests on Daikoku Island fluctuated (Appendix 1). 10) Pelagic Cormorant (Phalacrocorax pelagicus) This species was reported to breed on Moyururi Island (Abe & Matsuki 1968, Fujimaki 1986), Hanasaki-tateiwa (Abe & Matsuki 1968), Cape Esan (Kuroda 1958) and Teuri Island (Watanuki et al. 1986, Watanuki et al. 1988b, Fukuda et al. 1995). The number of active nests on Teuri Island increased by 7.1% annually during 1977-95 (Table 2), although the trend, shown by recent data, indicates that the population may remain stable (Teuri seabird group, unpublished data). Although this species was observed on the Pacific coast of eastern Hokkaido, our research is not enough to confirm any evidence of its breeding. 11) Streaked Shearwater (Calonectris leucomelas) In Hokkaido, the Streaked Shearwater breeds only on Oshima-ohoshima, (Watanuki et al. 1988b, Ogi et al. 1995) and 120-130 pairs bred there in 1995 (Ogi et al. 1995). 12) Leach's Storm-petrel (Oceanodroma leucorhoa) On Daikoku Island, 415,000-1,070,000 pairs bred in 1972-97 (Abe et al. 1972, Hayashida & Hashimoto 1981, Watanuki 1985, Kondo et al. 1991b, Niizuma 1995, Nakamura et al. 1997, Sato 1997). We think that several pairs of Leach's Storm-petrel bred at Daikoku-kojima near Daikoku Island in the 1970's, but now their breeding status is unknown. They were suspected to be breeding on Habomaimoshiri Island in 1987 (Sato 1988, Watanuki et al. 1988b), although their present status there is unknown.

2. Description of disturbances Out of the 14 colonies studied, disturbance by rats and cats was reported in five colonies, and disturbance by other animals was reported in four colonies (Table 3). Predation by gulls or crows was reported in 12 colonies, and other natural factors (prey resources, etc.) were reported in six colonies (Table 3). Slaty-backed Gulls prey on eggs, chicks, or adults of Black-tailed Gulls, Red-faced Cormorants, and Leach's Storm-petrels (Fujimaki 1961, Fujimaki et al. 1976, Hayashida & Hashimoto 1981, Watanuki 1982, 1983, Kosugi 1991, Kondo et al. 1991a, 1991b, Kondo 1992, Fukuda et al. 1995). Human persecution (egg collection, etc.) was reported in five colonies, and other human disturb- ances (sightseeing, etc.) were reported in six colonies (Table 3). At Teuri Island, people collected seabirds' eggs for food until the 1960's, and boats containing sightseers affected the breeding condition of Common Murres (Murata 1957, Terasawa et al. 1995). Death caused by being caught in commercial fishing nets was reported in eight colonies . Descriptions of natural and human disturbances on these six islands, Yururi Island, Moyururi Island, Teuri Island, Daikoku Island, Kiritappu-kojima and Oshima-ohoshima are summarized below, also with unpublished annual reports of conservation projects for endangered species of seabirds in Hokkaido (Hokkaido Government 1999, Ministry of the Status of Seabirds Breeding in Hokkaido 115 116 Yuichi Osa and Yutaka Watanuki

Environment, unpublished data). 1) Yururi and Moyururi Islands The nuisance of gulls and crows on breeding Tufted Puffins and Spectacled Guille- mots was reported. On Yururi Island, attacks by Black-tailed Gulls, Japanese Cormo- rants, and Peregrine Falcons, (Falco peregrinus) on adult flying or swimming Tufted Puffins have been observed (Kondo et al. 1986, Hokkaido Goverment 1999, Ministry of the Environment, unpublished data). Kondo et al. (1991a, 1991b) reported that rock blasting by kelp raisers deteriorated to nesting habitats of Red-faced Cormorants. Al- though the Nemuro City Board of Education limits landing on Yururi or Moyururi Islands, we observed picnickers visiting these islands, and photographers gave negative impact on breeding Tufted Puffins (Ministry of the Environment, unpublished data). Invasion of foxes and minks by crossing from the mainland on drift ices have been confirmed, which should be menace to gulls (Kondo unpublished data). The number of introduced rats increased very rapidly recently (Hokkaido Goverment 1999). Intensive fisheries by fishing nets set around these islands should have causes steady decrease of seabirds in this sea area (Kondo 2000). 2) Teuri Island In the 1950's people collected Rhinoceros auklets' eggs and hunted adult birds (Murata 1957). Predation by Slaty-backed Gulls and by Jungle Crows and Carrion Crows on the chicks of Common Murres was reported (Watanuki 1983, Terasawa et al. 1995). Slaty-backed Gulls also hunt the chicks and fledglings of Black-tailed Gulls and Rhinoceros Auklets. Moreover, crows take the eggs of these two species (Watanuki 1983). The introduction of cats and dogs into the breeding area of seabirds was reported before the 1980's (Hokkaido Institute of Environmental Sciences 1995), and many carcasses of chicks and adults of Black-tailed Gulls and Rhinoceros Auklets, presumably killed by cats, have been found since the 1990's (Hokkaido Institute of Environmental Sciences 1995), when the number of cats was estimated more than 1000. As there is a paved road along the edge of the colony, it is recognized that cars also accidentally kill the birds. The number of Common Murres decreased rapidly in the 1940's when the active coastal drift net of salmon fisheries began operating near the island, causing many murres entangled in the nets. 3) Daikoku Island Slaty-backed Gulls and crows are reported to prey on adult Leach's Storm-petrel (Watanuki 1986). Although the Board of Education of Akkeshi Town limits human landing on this Island, we are afraid that boats of sight visitors may approach too close to seabird colonies giving bad impacts to the birds. 4) Kiritappu-kojima It is possible that a mate of the Tufted Puffin pair that was breeding in 1996 was caught in a commercial fishing net, and this accident led to the failure of the pair to breed (Kataoka & Mizuno 1999). Slaty-backed Gulls breeding on the island are reported to snatch the fish from Tufted Puffins (Kataoka & Mizuno 1999). 5) Oshima-ohoshima Ogi et al. (1995) reported that Feral Rabbits (Oryctolagus cuniculus) took over the Status of Seabirds Breeding in Hokkaido 117 nests of Streaked Shearwaters, and that Norway Rats (Rattus norvegicus) preyed on their eggs. Fishermen are reported to have hunted the adult Streaked Shearwaters for food from the 1920's-1960's (Ogi et al. 1995).

Discussion Our review shows steady decreases (8.8-26.6% annually) of the Common Murre, Tufted Puffin and Spectacled Guillemot during the last 30 years in Hokkaido (Table 2). The number of breeding pairs of Red-faced Cormorants, Pelagic Cormorants, and Ancient Murrelets are less than 100 (Table 1). Based on criteria proposed by the Red List of Japan (Japan Environmental Agency 1998), these species, except for Pelagic Cormo- rants, are categorized as locally endangered species (CR: Common Murre, Tufted Puffin, Ancient Murrelet, and Red-faced Cormorant; VU: Spectacled Guillemot). The degrading conditions of breeding habitats are possibly a contributing factor to the decrease of these species (Table 3), although detailed information on the disturbance factors in breeding habitats is still lacking. Between the 1920's-1960's, egging and hunting by humans were potential threats (Murata 1957, Ogi et al. 1995), but these activities have been effectively controlled nowadays. Foxes, cats or rats introduced to these islands seriously impacted seabird colonies (Moor & Atkinson 1984, Peterson 1982, Bailey & Kaiser 1993, this study). Predation on seabird eggs and chicks by Slaty-backed Gulls and crows were reported in many colonies (Table 3). The increase in human waste or trash causes increase of gulls (Garthe et al. 1996, Oro et al. 1995), which is responsible to predation or prey-plunder to other breeding seabirds. Some amateur photographers carelessly approach the breeding nests of seabirds (Kataoka unpublished data). We need to prevent people from approaching seabird nests, through the breeding season (Ogi 1997). We also need to develop and implement a comprehensive plan to monitor seabird colony conditions over the entire Hokkaido area (Hokkaido Government 1999). The Ministry of the Environment designated many colonies as Wildlife Protection Areas, and the "Wildlife Protection and Hunting Law" prohibits the free-capture of wild animals. Moreover, seven colonies have also been designated as national parks or natural monuments by the Ministry of the Environment or the Ministry of Education and Science. However, these systems do not prevent fishing in the important feeding or wintering sea areas of seabirds (Ogi 1995, Oka 1995, Sato 1995a). Seabirds are long-lived animals with high annual survival rate (80-94%, Wooler et al. 1992), and loss of adult birds caused by fishing net accidents is an important factor for maintenance of breeding population (Croxall & Rothery 1991). Mortality by fishing nets is reported to impact the albatross and alcid populations (Brothers 1991, de la Mare & Kerry 1994, Moloney et al. 1994, Kalmer et al. 1996, Carter & Sealy 1984, Jones & DeGange 1988), although the impact of Japanese offshore drift net upon shearwaters is not so serious (Ogi 1984). Kataoka & Mizuno (1999) proposed a protected sea area for the Tufted Puffins breeding at Kiritap- pu-kojima. For the sustainable fishing industry, we must develop fishing techniques which should minimize the impact on the marine ecosystem. For example, nets with larger mesh, would release small fishes, which are fed by seabirds (Dully & Schneider 1994, Garthe et 118 Yuichi Osa and Yutaka Watanuki

al. 1996, Furness 1992), thus allowing coexistence of seabirds and fishing industry. Fishing gear and techniques should also be improved to decrease seabird bycatches (Ogi 1987, Brothers 1996, Cherel et al. 1996, Melvin & Conquest 1996). Some non-fishing areas are to be considered to provide feeding sea area for seabirds. The chemical pollution of the sea is now important threat to marine life of seabirds (Clark 1992, Elliot & Noble 1993, Ohlendorf 1993). Recently, oil spills of ships have become occasional serious factor to local population of seabirds (Burger & Fry 1993, Oka et al. 1999). In 1996, the Nakhodka (Russian tanker) oil spill in Japan Sea killed 2,800-3,500 Rhinoceros Auklets at sea (Nippon Foundation 1998, Japan Alcids Group 1998), although serious effect to its breeding population on Teuri Island was not reported. On the coast of Russian Sakhalin, an oil development project is being progressed. Seabird protection should be advanced by exchanging information between Russian and Japanese researchers and governments.

Acknowledgments

We are grateful to Ms. Sung Saiha for useful comments on our manuscript and Mr. J. Chishima, Mr. Y. Hayashi, Mr. Y. Kataoka, Mr. N. Kondo, Mr. S. Konno, Ms. R. Murayama, and Mr. T. Shibuya for their kindness of providing unpublished data. This research is funded by the Japan Environmental Agency.

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Watanuki, Y. 1995. Long-term trands of seabirds' populations on Teuri Island. In Report on the Seabirds' Community Survey at Teuri Island 1992-1994. (ed. Hokkaido Institute of Environmental Science), pp. 39- 42. Hokkaido Institute of Environmental Science, Sapporo. (In Japanese) Watanuki Y., M. Aotsuka & T. Terasawa. 1986. Status of seabirds breeding on Teuri Island. Tori 34: 146-150. (In Japanese with English abstract) Watanuki Y., M. Aotsuka, T. Terasawa & H. Abe. 1988a. The status of the Common Murre on Teuri Island. In Report on the Ecology of Common Murre Survey at Teuri Island 1987. (ed. Hokkaido Nature and Conservation Section), pp. 29-52. Hokkaido Nature and Conservation Section, Sapporo. (In Japanese) Watanuki, Y., N. Kondo & H. Nakagawa. 1988b. Status of Seabirds breeding in Hokkaido. Japanese Journal of Ornithology. 37: 17-32. (In Japanese with English abstract) Wooler, R. D., J. S. Bradley & J. P. Croxall.1992. Long-term population studies of seabirds. TREE 7:111-114.

北海道における海鳥類繁殖地の現状

北海道 の海鳥類 の保護及 び研究 を進め るため に,既 存の調査報告書 を収集 して,飛 来数 ある いは繁殖つ がい数 とい った繁殖地 サイズの動 向 と海鳥類の繁殖 に対す る人為的攪乱及 び自然界 で の攪乱 につ いて分析 を行 った。 北 海 道 で は 少 な く と も12種 の 海 鳥 類 が 繁 殖 し て い る。 繁 殖 規 模 の 概 数 は,ウ ミガ ラ ス(Uria aalge),10つ が い 以 下;エ ト ピ リカ(Lunda cirrhata),15つ が い;ケ イ マ フ リ(Cepphus carbo),100 つ が い;ウ ミ ス ズ メ(Synthliboramphus antiquus),20つ が い 以 下;ウ ト ウ(Cerorhinca monocerata), 300,000つ が い;オ オ セ グ ロ カ モ メ(Larus schistisagus),10,000つ が い;ウ ミ ネ コ(Larus crassir- ostris),30,000つ が い;チ シ マ ウ ガ ラ ス(Phalacrocorax urile),25つ が い;ウ ミ ウ(Phalacrocorax capillatus),3,000つ が い;ヒ メ ウ(Phalacrocorax pelagicus),10つ が い;オ オ ミ ズ ナ ギ ド リ(Cal- onectris leucomelas),120つ が い;コ シ ジ ロ ウ ミ ツ バ メ(Oceanodroma leucorhoa),900,000つ が い で あ っ た 。 そ の 他 に マ ダ ラ ウ ミス ズ メ(Brachyramphus perdix)の 繁 殖 に つ い て は 不 明 で あ る 。 天 売 島 の ウ ミガ ラ ス 繁 殖 地 に い た 成 鳥 数 は,1938年 か ら1980年 の 間 に 年 平 均 で12.2%ず つ 減 少 して お り,1981年 か ら1994年 の 間 に は 年 平 均 で26.6%ず つ 減 少 し,1998年 に は7つ が い が 確 認 さ れ た に 過 ぎ な い 。 モ ユ ル リ島 の ウ ミガ ラ ス に っ い て,そ の 繁 殖 地 に い た 成 鳥 数 は1965 年 か ら1985年 ま で に 年 平 均 で24.8%ず つ 減 少 し た が,1985年 以 来 飛 来 個 体 が 確 認 さ れ て お ら ず,繁 殖 地 が 消 失 し た と 考 え る 。 さ ら に モ ユ ル リ島 エ ト ピ リカ 繁 殖 地 周 辺 に い た 成 鳥 数 は1960 年 か ら1995年 の 間 に 年 平 均 で10.0%ず つ 減 少 し て お り,現 在 で は ユ ル リ ・モ ユ ル リ島 を 中 心 に15つ が い 前 後 が 繁 殖 して い る と 考 え られ る 。 ケ イ マ フ リで は,天 売 島 に お い て 年 平 均8.8% ず つ,ユ ル リ島 に お い て は14.4%ず つ 減 少 して お り,北 海 道 全 体 の 生 息 数 も100つ が い 程 度 と 考 え られ る こ と か ら,こ の 減 少 傾 向 が 続 く と繁 殖 地 の 消 失 も考 え ら れ る 。 そ の 一 方 で,モ ユ ル リ島 の ウ トウ 繁 殖 地 サ イ ズ は1960年 か ら1996年 の 間 で 年 平 均14.2%ず つ 増 加 し て い た 。 過 去30年 間 の 間 に オ オ セ グ ロ カ モ メ は 増 加 傾 向 に あ る と 考 え られ た が,モ ユ ル リ島 の 繁 殖 地 サ イ ズ は1982年 か ら 減 少 に 転 じ,1996年 ま で で 年 平 均7.0%ず つ 減 少 して い た 。天 売 島 の ウ ミ ネ コ は,1980年 代 に は3万 つ が い が 営 巣 し て い た が,ネ コ等 の 捕 食 に よ り1990年 代 に 半 減 し た 。 そ の 一 方 で 利 尻 島 の ウ ミネ コ は1987年 に 新 た な 繁 殖 地 が 形 成 さ れ て 以 来,年 平 均19.5%ず つ

増 加 し,現 在 で は1万 つ が い 以 上 が 営 巣 す る に 至 っ て い る 。 調査報告書 に攪乱 の記述 のあ る繁殖地 は14箇 所 であ った。 カモメ類 あ るいはカ ラス類 によ る攪乱の記述が あ ったのは12箇 所,死 因が漁網 への混獲 との記述が あったの は8箇 所,人 為導 入 され た ドブネズ ミ類あるいはネ コによる攪乱 の記述 があ ったの は5箇 所 であ った。 124 Yuichi Osa and Yutaka Watanuki

日本 の海鳥類繁殖地 の多 くは,鳥 獣保護及狩猟 ニ関 スル法律等 によ って保護 されて いる。 し か しなが ら,繁 殖地周辺 の採 餌域 あるいは越冬域 とい った場所 は保護 の対 象 とな って いない。 その ため,海 鳥が混獲 しに くい漁具を開発す ることや,繁 殖地周辺での漁業活動 を見 直す こと, あるいは石油流 出事故 に対 応す るたあの体制構築 の必要 があろ う。 また,人 間 によって繁殖地 に導入 され た,あ るいは人間の出す ゴ ミによ って増加 した ドブネズ ミ,ネ コ,カ モメ類,カ ラ ス類等 の影響 について考 え る必要が あろ う。

長 雄一:北 海道環境科学研究 セ ンター自然環境部野生動物科,〒060-0819北 海道札幌市北 区北19条 西12丁 目. 綿貫 豊:北 海道大学大学 院農学 研究科動物生態学分野,〒060-8589北 海道札 幌市 北9条 西 9丁 目. Status of Seabirds Breeding in Hokkaido 125

Appendix 1. Number of breeding pairs and adults of seabirds in Hokkaido. In columns of "No. of pairs", "Br" indicates the case in which breeding was confirmed, but number of breeding pairs is not accurate. In columns of "Method", a. The researcher counted the number of all individuals or pairs in a colony; b. The researcher made local sampling counts, and estimated the entire numbers of birds of a breeding colony; c. The researcher estimated very roughly the number of individual or pairs; d. The researcher counted the number of individuals at sea around the colony. 126 Yuichi Osa and Yutaka Watanuki

Appendix 1. (Continued) Status of Seabirds Breeding in Hokkaido 127

Appendix 1. (Continued) 128 Yuichi Osa and Yutaka Watanuki

Appendix 1. (Continued) Status of Seabirds Breeding in Hokkaido 129

Appendix 1. (Continued) 130 Yuichi Osa and Yutaka Watanuki

Appendix 1. (Continued) Status of Seabirds Breeding in Hokkaido 131

Appendix 1. (Continued) 132 Yuichi Osa and Yutaka Watanuki

Appendix 1. (Continued) Status of Seabirds Breeding in Hokkaido 133

Appendix 1. (Continued) 134 Yuichi Osa and Yutaka Watanuki

Appendix 1. (Continued) Status of Seabirds Breeding in Hokkaido 135

Appendix 1. (Continued) 136 Yuichi Osa and Yutaka Watanuki

Appendix 1. (Continued) Status of Seabirds Breeding in Hokkaido 137

Appendix 1. (Continued) 138 Yuichi Osa and Yutaka Watanuki

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Appendix 1. (Continued) 140 Yuichi Osa and Yutaka Watanuki

Appendix 1. (Continued) Status of Seabirds Breeding in Hokkaido 141

Appendix 1. (Continued)