9 巻 (2010) 1 号 p. 37-48
We report the results of a 15-year bird census conducted on the Hokkaido University campus in Sapporo city. A standardized route census was carried out monthly by the students of the Hokkaido University Birding Club (HUBC). Bird species were classified according to their migratory status as: long-distance migrants (LDM), short-distance migrants (SDM), winter visitors (WV) and residents (R). Of a total of 88 species of birds identified, 18 were Rs, 21 LDMs, 26 SDMs and 10 WVs. The overall bird abundance for the R group was greatest, however this was strongly affected by fluctuations in the Eurasian Tree Sparrow Passer montanus population, representing more than half of the total bird abundance. This species declined sharply in 2006, and has not recovered yet. LDMs declined in both species richness and bird abundance, whereas SDMs and WVs had fluctuated annually in their abundance. Three major tendencies were detected by comparing nationwide changes of bird communities with those of the study site. 1) Overall population declines in the wintering and stopover grounds, which were aggravated by habitat degradation in the breeding grounds of the study site (White-throated Needletail Hirundapus caudacutus, Black-faced Bunting Emberiza spodocephala, Oriental Turtle Dove Streptopelia orientalis), 2) Nationwide population increase while the population declined in the study site due to intensified management of vegetation (Great Tit Parus major, Great Spotted Woodpecker Dendrocopos major), 3) Population increases in species adapted or adapting to human landscapes (Large-billed Crow Corvus macrorhynchos, Mallard Anas platyrhynchos, Slaty-backed Gull Larus schistisagus). In addition, the drastic decline of Eurasian Tree Sparrows in early 2006 was caused by a local die-off event apparently due to an infectious disease. General recognition of the academic and conservation importance of a long-term census is hoped to enhance motivation for and efforts towards a census in various areas.