Regional population trend of common wintering waterfowl in Japan, from 1996 to 2009

Abstract

We analyzed population trends of 13 species of wintering waterfowl during a 14-year period (1996-2009) in each of 47 prefectures in Japan. We used data from annual volunteer-participatory waterfowl surveys, which were conducted in Japan by the Ministry of the Environment and local prefectural governments. Population indices and long-term trends of each species were calculated using TRIM (TRends and Indices for Monitoring data). The populations of Mallard Anas platyrhynchos and Eurasian Teal Anas crecca were found to have declined in many regions or prefectures while Tufted Duck Aythya fuligula and Greater Scaup Aythya marila increased nationwide. The Eurasian Wigeon Anas penelope population remained stable throughout the country. Populations of nine species declined in the Kanto region, and eight species declined in the Chubu region. In contrast, eight species showed population increases in the Kinki region and five species increased in the Chugoku and Shikoku regions. We discuss the possibility that changes in breeding or wintering habitat and global warming may have affected the distributions of many duck species of the January during the study period.