Gorsachius goisagi breeds in Japan. There has been one report of breeding from Taiwan (China), and recent work has discovered a breeding site at Jeju Island, South Korea (Oh et al. 2010). It has also been recorded in spring and summer in Russia (Primorye and Sakhalin), and is a passage migrant in coastal mainland China and Hong Kong (China), and also in Taiwan. The main wintering area appears to be in the Philippines, but it has also been recorded as a non-breeding visitor to Indonesia, and as a vagrant to Brunei and Palau. Improved awareness of the identification criteria for immatures of this species has led to a marked increase in records from the Philippines (D. Allen in litt. 2012). It was apparently locally common in Japan until the 1970s, but by the 1980s and 1990s had disappeared from many of its former breeding sites. There have apparently been just two records from mainland China since the early 1960s, one of two sightings at Wuyuan in Jiangxi Province in April 2006 and a taxidermy specimen noted in Haiyan county in Zhejiang province in February 2010 and apparently purchased in Haining city in April 1998 (He Fenqi in litt. 2007, 2012). The relative paucity of recent records suggested that the population numbered fewer than 1,000 mature individuals, but recent work in Japan and increasing numbers of records from the Philippines imply that this may have been overly pessimistic. Hence, the true figure may lie within the band 1,000-2,499 individuals. However, this may still be an underestimate (K. Kawakami in litt. 2012).