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[F-2.2 Study on the mechanism of the population decline of long-distance migratory birds in Japan]

[Contact Person]

Hiroyoshi Higuchi
Professor
Laboratory of Wildlife Biology
School of Agriculture and Life Sciences
The University of Tokyo
Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657
Phone:+81-3-3812-2111 ext.7541, Fax:+81-3-5689-7254
E-mail:higuchi@uf.a.u-tokyo.ac.jp

[Total Budget for FY1995-FY1997]

17,000,000 Yen (FY1997;5,687,000 Yen)

[Abstract]

In order to show the population trend of forest and wetland summer visitors to Japan, field observations, literature surveys, and questionnaire surveys were conducted in 1995-1997. Field observations and literature surveys showed that the number of seven species of summer visitors drastically declined in some areas of Japan: Black Paradise Flycatchers Terpsiphone atricaudata, Ashy Minivets Pericrocotus divaricatus, Yellow-breasted Buntings Emberiza aureola, Ruddy Kingfishers Halcyon coromanda, Brown Hawk Owls Ninox scutulata, Jungle Nightjars Caprimulgus indicus, and Porzana Crakes Porzana fusca.

These seven species were the focus of questionnaires sent to the members of the Wild Bird Society of Japan. It was shown that all these species declined in many areas of Japan during the past 25 years, although the pattern of decline varied somewhat by species. Natural and artificial wetlands, the breeding habitat of Porzana Crakes, had been destroyed or altered in many of the areas, suggesting that habitat destruction in Japan is the main reason for the decline of the crakes. However serious habitat destruction and deterioration did not occur in half of the study areas of the other six forest and grassland species. Long-term observation records showed that in many areas the number of species decreased in summer visitors but did not change or increased in residents. It seems that the population decline of summer visitors is mostly associated with habitat destruction in their wintering areas of Southeast Asia.

Field and reference surveys were conducted in Sumatra, Java, Kalimantan, and Singapore. Tropical rainforests had been extensively cut in many of these wintering areas, and Japanese summer visitors were not observed there. Useful references and information could not be found for the population trends of these birds.

Some recommendations are proposed for further research and conservation in Japan and other Asian countries.

[Key Words]

Conservation, Migration, Population decline, Summer visitor, Tropical rainforest