Pacific Science (1995), vol. 49, no. 1: 69-86 © 1995 by University of Hawai'i Press. All rights reserved Distribution and Ecology of Birds of Japan! H!ROYOSHI HIGUCHI,2 JASON MINTON,3 AND CHIEKO KATSURA4 ABSTRACT: The effects of island biogeography are clearly seen in the avi­ fauna ofJapan. Species composition and distribution reflect Japan's geographic, climatic, vegetational, topographical, and geological characteristics. It is a country composed primarily of mountainous, forested islands that lies off the coast ofa continent rich in bird life. Though Japan has a wide range ofclimates and diverse forest habitats, the terrestrial and freshwater avifauna is de­ pauperate when compared with species, family, and order diversity on the nearby continent, which is both larger in total area and more diverse in hab­ itats. However, the bird groups that do have higher species diversity in Japan than in the Asian mainland are seabirds. The large, productive ocean area and small, isolated islands provide them with foraging and nesting sites, and the long geographic range of Japan allows seabirds from both northern and southern regions to nest in the Islands. Island biogeography also affects the ecology of many terrestrial species. Niche shift and expansion of foraging and parasitic behaviors are seen in populations established on islands where the species composition does not include certain competitors. The terrestrial species resident on small islands have developed unique breeding behavior, in com­ parison with their conspecifics on larger islands, such as smaller clutch size, exaggerated begging behavior, and longer parental care in small-island pop­ ulations of Varied Tits, Parus varius Temminck & Schlegel. JAPAN LIES ALONG the east side of the Asian species distribution. Second, the species continent. The long island chain stretches composition of Japan is compared with that from Hokkaido in the north to the South­ of the Asian mainland. We pay particular West Islands in the south (Figure 1). The attention to the composition at the order, characteristics of Japanese avifauna have family, and species levels. The comparison been described (e.g., Blakiston 1883, Austin yields differences that are explained by the and Kuroda 1953, Brazil 1991), but most of differences in area sizes and habitat between those authors focused on taxonomic aspects Japan and the mainland. and did not discuss ecological relationships. Last, we report some ecological phenom­ The distribution and ecology of birds are af­ ena from our fieldwork. Characteristics such fected by the environmental features of birds' as foraging and breeding behavior are in­ habitat. fluenced by the presence or absence of other In this paper, we review the characteristics competing species. Species existing in areas of Japanese avifauna from the ecological without competitors show ecological shifts point of view. First, we describe the physical with morphological changes allowing them environment on which the Japanese avifauna to take advantage of resources left available depends; then we examine its influence on by the absence of competition. Further, breeding behavior changes for large- and small-island p_opulationsare described, and 1 Manuscript accepted 27 April 1994. climatic explanations are suggested. 2Laboratory of Wildlife Biology, University of To­ kyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113, Japan. 3Research Center, Wild Bird Society of Japan, 15-8 Features ofthe Japanese Environment Nanpeidai, Shibuya-ku, Tokyo 150, Japan. 4 Japan-China Cooperative Institute for Ornithology, The Japanese island chain and the Asian Nagahama 1-2-6-505, Chuo-ku Fukuoka 810, Japan. continent are separated by the Japan Sea, at 69 Russia Japan Sea Island China Islands Tokara Ogasawara Islands Daito Islands ... .. i;,<I. Pacific Ocean FIGURE 1. Japan,neighboring islands, and nearby continental Asia. ##1 FUh. £fMS¥:;4HP ¥ WAG Distribution and Ecology of Birds of Japan-HIGUCHI ET AL. 71 distances ranging from 200 to 800 kIn. The main types, broad-leaved evergreen forests in more than 3,500 Japanese Islands cover an the south and deciduous forests in the north. area from Sakhalin in the north, to Taiwan in The majority of Hokkaido and adjacent is­ the south, the Kurile Islands in the east, and lands is vegetated with typically subarctic the Korean Peninsula in the west. mixed forest of deciduous and coniferous The shapes and sizes of the Japanese Is­ trees. lands have changed many times in geologic There are both warm and cold currents in history, and most of the Japanese Islands the ocean surrounding Japan. Kuroshio, a were connected to the Asian continent at one southern warm current, flows north and di­ time (Minato et al. 1965). Honshu, Shikoku, vides at the southern tip of Kyushu, flowing and Kyushu were isolated from the continent into both the Sea of Japan and the Pacific and from Hokkaido, which was the last main Ocean. The cold Oyashio Current moves island to be separated from the continent, south from the subarctic, along the coast of after the latest Pleistocene of ca. 20,000 yr eastern Hokkaido and northern Honshu. ago. Since that time, all the islands have been These interacting currents have made the isolated from the continent and from each coastal and marine regions of Japan ex­ other. tremely productive (Ching 1991). Japan's terrestrial habitat is heavily vege­ tated. Forests cover 68% of the land area. Features ofthe Avifauna Relative to The topography of Japan is extremely Environmental Features mountainous, with 70% of the land area in mountain ranges. The altitudinal range is The distribution of avifauna in Japan is from sea level to 3,776 m. a function of the physical environment, Japan lies in three climate zones because particularly its island nature. The avifauna of its long north-south geographic range, of the Islands varies seasonally and region­ between 24° and 46° N latitude. There are ally. However, forest species predominate subtropical, temperate, and subarctic climate throughout the Islands. The forest landscape regions. The Ryukyu Islands, which are the supports a majority of Japan's terrestrial bird southernmost islands of the Japanese island species. Approximately 100 of the 150 land chain, lie in the subtropical zone. The islands and freshwater bird species are woodland extending northward from the Ryukyus to dwellers, such as hawks, pheasants, wood­ the southern tip of Kyushu are called the peckers, thrushes, warblers, flycatchers, South-West Islands. The majority of the finches, and buntings. main islands and land area of Japan lies in The seasonal climate of much of Japan the temperate zone. Northern Hokkaido and means that many species are migratory. several associated islands belong to the sub­ Some are winter or summer visitors, and arctic region north of45° N latitude. others, such as shorebirds, visit Japan only as The southern South-West Islands are cov­ a migration stopover. Thus, Japan's species ered with subtropical broad-leaved and man­ composition changes between summer and grove forests. The northern South-West Is­ winter. The number of species that arrive lands are covered with temperate mixed each season closely matches the number that evergreen forests intergrading with typically leave during the period (Figure 2). southern vegetation. In this latitudinal range, Regional species composition results from but to the east and much more remote, are the geographic situation of the area. The avi­ the Daito and Ogasawara (Bonin) Islands. fauna of the South-West Islands is influenced They are on the order of 1000 kIn from the by the tropical area and temperate regions. large northern islands of Japan and have no Tropical species such as the einmrmoll neighbors within 500 kIn. Bittern, Ixobrychus cinnamomeus (Gmelin); The temperate zone includes most of the Malay Night Heron, Gorsakius melanolophus main islands of Kyushu, Shikoku, Honshu, (Raffles); Purple Heron, Ardea purpurea L.; and southern Hokkaido, between 31 ° and 42° Barred Buttonquail, Turnix suscitator N latitude. The vegetation consists of two (Gmelin); White-breasted Waterhen, Amaur- 72 PACIFIC SCIENCE, Volume 49, January 1995 N=536 • Resident II Winter visitor ~ Summer visitor 12] Transient 12] Straggler FIGURE 2. Residential status of Japanese birds as a proportion of five categories. Based on Wild Bird Society of Japan (1982) and Takano (1985). ornis phoenicurus (pennant); and Red-capped The distribution of species within each region Green Pigeon, Sphenurusformosae (Swinhoe) varies. Island size, island distance from emi­ (Brazil 1991), intergrade with Palearctic spe­ gration sources, and chance, as well as island cies such as Woodcock, Scolopax rusticola geology have determined the presence or ab­ L.; Japanese Robin, Erithacus akahige sence of species. The number of species on (femminck); and Carrion Crow, Corvus co­ each island differs. For example, in the rone L., in the northern South-West Islands. South-West Islands, 47 species have been In the subarctic region of Hokkaido, identified as resident, but only 17 of these are drastic seasonal variation in temperature found on five or more ofthe six major islands drives many birds south for the winter. But of this group (Ikehara 1991). Figure 3 shows many breeding and resident species of Hok­ the species-area relationship of the Japanese kaido are closely related to the northern cli­ Islands. The number of breeding species in­ mate and do not live elsewhere in Japan. The creases as the area of an island increases. White-tailed Sea Eagle, Haliaeetus albicilla However, in remote islands more than 300 (L.); Common Merganser, Mergus merganser km distant from any main island of Japan, L.; Tufted Puffin, Lunda cirrhata (pallas); fewer species are present than expected from Hazel Grouse, Tetrastes bonasia (L.); Blakis­ the size of the island. These are good exam­ ton's Fish Owl, Ketupa blakistoni (Seebohm); ples of island biogeographical theories Three-toed Woodpecker, Picoides tridactylus (MacArthur and Wilson 1963, 1967). (L.); and Willow Tit, Parus palustris L., are The relationship between island size, re­ breeders not seen south of Hokkaido.