2020 Volume 16 Pages A47-A58
A change of distribution for birds in Hokkaido is evident from results of the National Surveys on the Natural Environment (the report of the distribution of Japanese birds) between 1974-1978 and 1998-2002. As a series of nationwide reports, the published distribution maps were not suitable for showing regional patterns, so I analyzed the data on range changes of each bird species in Hokkaido, the northernmost region of Japan. Range reductions were observed for some, but not all, summer migrant birds, and severe range reductions were confirmed in particular species. Resident birds, on the other hand, experienced fewer range reductions, and a higher frequency of range expansions. Summer migrant birds showed range reductions in several habitat types, including grasslands, rural areas, and woodlands. The species that showed range expansions primarily inhabited woodlands, whereas those inhabiting grasslands and rural areas had low frequency of expanded ranges. A severe range reduction was observed for three species: White-throated Needletailed Swift Hirundapus caudacutus, Brown Shrike Lanius cristatus, and Yellow-breasted Bunting Emberiza aureola. Oddly, the range of Ruddy Kingfisher Halcyon coromanda, which showed a nationwide range expansion, had a range reduction in Hokkaido. Range reduction was not confirmed for four species that have been reported in previous studies, namely Latham's Snipe Gallinago hardwickii, Bull-headed Shrike L. bucephalus, Eurasian Skylark Alauda arvensis, and Eurasian Tree Sparrow Passer montanus. Further study of ranges and population trends for birds in Hokkaido is recommended, as the data shows there have been numerous changes in the distribution of birds in the region.
