Effects of climatic conditions on the northward expansion of the wintering range of the Greater White-fronted Goose in Japan

Abstract

The Greater White-fronted Goose Anser albifrons has recently begun to winter at Lake Otomonuma (Akita Prefecture), a migratory stop-over site located 180 km northwest of its main wintering site at Lake Izunuma–Uchinuma (Miyagi Prefecture), in northern Honshu, Japan. Data collected over a 17-year period (from 1987/1988 to 2003/2004) have allowed us to analyze factors influencing the large-scale redistribution of this species. The number of geese in Akita increased during November and December, but decreased in January. The number of geese wintering in Akita from November to December was not correlated with the number wintering in Miyagi; therefore, migration from the breeding area or from northern staging sites seems to have caused the population to increase in Akita in December. The population in Akita decreases with low temperatures in January; however, the decrease in Akita was not correlated directly with an increase in Miyagi from December to January as the geese also visit other more southerly areas in addition to Miyagi. In fact, we found no significant correlation between the size of the goose population in Akita and climatic conditions during November and December. Our analysis demonstrated that the use of Akita by Greater White-fronted Goose in winter was attributed to density-independent effects regardless of the population fluctuation in Miyagi from November to December, and to severe weather conditions in January forcing the geese to move from Akita to a southern refuge.