Justification of Red List Category
This species has a very small, declining population, and therefore qualifies as Endangered. Declines are primarily a result of deforestation in its breeding and wintering ranges.
Recent work in Japan suggests the previous assertion that the global population comprises fewer than 1,000 individuals may have been overly pessimistic (although Brazil 2009 estimated fewer than 100 breeding pairs, fewer than 50 individuals on migration and fewer than 50 wintering individuals in Japan). Hence, the true figure probably lies within the band 1,000-2,499 individuals. This equates to 667-1,666 mature individuals, rounded here to 600-1,700 mature individuals.
Rapid declines in the past are suspected to be on-going, mainly owing to forest loss and changing agricultural practices.
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. There may also be a small resident flock in inland mainland China (He et al. 2016). 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).
It breeds in heavily forested areas, including coniferous, broadleaved and degraded forest, on hills and the lower slopes of mountains (up to 1,500 m), where there are watercourses and damp areas. It winters in dark, deeply shaded forest near water up to 2,400 m. It forages mainly in forest, but will use swamps, rice-fields and farmland and is mainly crepuscular. Breeding has been recorded from April to July (Kawana 2006). A habitat model showed that precipitation and the number of abandoned rice fields were good predictors of occurrence for this species, with this habitat likely providing food source and nesting trees. Forest plantations were negatively associated with species occurrence (Hamaguchi et al. 2014). Earthworms are probably the principal food source, but land snails, cicadas, crabs, and ground and scarabid beetles are all present in its diet (Kawakami et al. 2005, K. Kawakami in litt. 2007, Oh et al. 2010).
The main threat is deforestation for timber and agriculture in both its breeding and non-breeding ranges. The development of dense scrub undergrowth in forest and on abandoned farmland (following a change in traditional agricultural practices) is believed to reduce the suitability of these habitats for feeding. It has probably been hunted in many parts of its range and suffers from human disturbance (Anon. 2009). It declined rapidly on Miyake-jima in the Izu Islands, where it was formerly abundant, following the introduction of Siberian weasel Mustela sibirica in the early 1970s. Today nest predation by corvids is an increasing threat as crow populations increase in urban and suburban areas.
Conservation Actions Underway
It is legally protected in Japan and Hong Kong. Birds may occur in protected areas in Japan and it has been recorded in Quezon National Park, Philippines. Environmental Impact Assessments are conducted prior to major developments in Japan, and if this species is identified using a site mitigation measures are taken (K. Kawakami in litt. 2007).
49 cm. Small, stocky heron with stout bill. Rufous-brown head and neck. Black streaks down foreneck and breast. Chestnut-brown upperparts and wing-coverts with fine black vermiculations. Juvenile and immature has blackish crown, less rufous on head, more streaked neck, paler wing-coverts and white in primaries. Similar spp. Malayan Night-heron G. melanolophus has black cap and long crest, and shows white in primaries when flying.
Text account compilers
Benstead, P., Bird, J., Chan, S., Crosby, M., Khwaja, N., Peet, N., Taylor, J., Martin, R, North, A.
Kominami, Y., Kawakami, K., Allen, D., He, F.
BirdLife International (2020) Species factsheet: Gorsachius goisagi. Downloaded from http://www.birdlife.org on 26/11/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/11/2020.