• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	-	C2a(ii)

Red List history

Year	Category	Criteria
2020	Vulnerable	C2a(ii)
2016	Endangered	C2a(i)
2012	Endangered	C2a(i)
2008	Endangered	C2a(i)
2004	Endangered
2000	Endangered
1996	Vulnerable
1994	Vulnerable
1988	Threatened

Migratory status	full migrant	Forest dependency	high
Land-mass type	continent	Average mass	-

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	1,010,000 km2	medium
Extent of Occurrence (non-breeding)	1,440,000 km2	medium
Number of locations	11-100	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	5000-9999 mature individuals	poor	suspected	2014
Population trend	decreasing	poor	inferred	2010-2026
Rate of change over the past 10 years/3 generations (longer of the two periods)	1-9%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	1-9%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	1-9%	-	-	-
Generation length	5.5 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: Previous work in Japan suggests the assertion that the global population comprises fewer than 1,000 individuals may have been overly pessimistic. These estimations are however not considered accurate by some researchers (K. Kawakami in litt. 2016). Recent mating call detections however recorded 23 individuals per 100 km² in rural secondary forests across the Aichi Prefecture in central Japan (Hamaguchi et al. 2014). The total area of rural secondary forests in Honshu, Kyushu and Shikoku islands estimates to 72,000 km² (Watanabe et al. 2012). Thus, the number of mature individuals is thought to be approximately 8,280. However, mating call detection studies have been considered as an unreliable method of monitoring breeding numbers in this instance due to the species's inconspicuous habits and the potential of receiving duplicated records (K. Ohata in litt. 2020). Similar calling surveys have for example not recorded any nests, and as such breeding birds, despite observing other calling individuals. It is also likely that surveys specific to limited sites (the Aichi area in this instance), may not yield results that are compatible with other suitable habitats across the species's range (K. Ohata in litt. 2020). Habitat models have additionally been considered impractical methods of estimating population numbers or trends (J. Kushlan in litt. 2020). Hence, to account for any uncertainty, the true figure is placed here in the band of 5,000-9,999 mature individuals, roughly equating to 7,500-15,000 individuals. As per the Waterbird Population Estimates, the species is also thought to occur in only one flyaway population across Eastern and South-eastern Asia (Wetlands International 2020). This is assumed to represent one subpopulation holding all mature individuals.

Trend justification: The species had previously considered to have undergone rapid declines due to deforestation and habitat conversion (Martinez-Vilalta et al. 2020). However, recent forest loss estimates show a negligible decline (Tracewski et al. 2016, Global Forest Watch 2020), equating to 3% over three generations (16.5 years; Bird et al. 2020). Forest destruction is also considered to no longer be a threat across breeding sites in Japan (S. Chan in litt. 2020). However, the population is thought to be rapidly declining at migratory and wintering grounds (S. Chan in litt. 2020), primarily owed to hunting pressure. Breeding areas may also suffer from problematic native and non-native species, as well as some level of continued habitat degradation. Thus, the population is inferred to be undergoing a continued decline of 1-9% over three generations.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Brunei	extant	vagrant			yes
China (mainland)	extant	native	yes			yes
Hong Kong (China)	extant	native				yes
Indonesia	extant	vagrant			yes
Japan	extant	native		yes
Palau	extant	vagrant			yes
Philippines	extant	native			yes
Russia	extant	vagrant			yes
Russia (Asian)	extant	vagrant			yes
South Korea	extant	native		yes	yes
Taiwan, China	extant	native				yes
Vietnam	extant	vagrant

Country/Territory	IBA Name
Indonesia	Tangkoko Dua Sudara
Indonesia	Mahawu - Masarang
Philippines	University of the Philippines Land Grants (Pakil and Real)
Philippines	Quezon National Park
Philippines	Victoria and Anepahan Ranges
Philippines	Central Panay mountains
Philippines	Cuernos de Negros
Philippines	Mount Bandila-an
Philippines	Mount Hilong-hilong
Philippines	Mount Kampalili-Puting Bato
Philippines	Mount Hamiguitan (Tumadgo peak)
Philippines	Liguasan marsh
Philippines	Mount Busa-Kiamba
Philippines	Mount Latian complex
Philippines	Pasonanca watershed
Philippines	Mount Malindang
Japan	Hachirogata
Japan	Mount Hyonosen

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Artificial/Terrestrial	Arable Land	suitable	non-breeding
Forest	Subtropical/Tropical Dry	suitable	non-breeding
Forest	Subtropical/Tropical Dry	suitable	breeding
Forest	Subtropical/Tropical Moist Lowland	major	non-breeding
Forest	Subtropical/Tropical Moist Lowland	major	breeding
Forest	Subtropical/Tropical Moist Montane	major	non-breeding
Forest	Subtropical/Tropical Moist Montane	major	breeding
Forest	Temperate	major	breeding
Wetlands (inland)	Bogs, Marshes, Swamps, Fens, Peatlands	suitable	non-breeding
Altitude	0 - 2400 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Shifting agriculture	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Hunting & trapping terrestrial animals - Intentional use (species is the target)	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species mortality
Biological resource use	Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Ecosystem degradation
Energy production & mining	Renewable energy	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Geological events	Volcanoes	Timing		Scope		Severity		Impact
		Past, Likely to Return		Minority (<50%)		Rapid Declines		Past Impact
		Stresses Ecosystem degradation, Ecosystem conversion
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Mustela sibirica	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Unspecified species	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Cervus nippon	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Causing/Could cause fluctuations		Low Impact: 5
		Stresses Species disturbance, Ecosystem conversion, Reduced reproductive success
Residential & commercial development	Commercial & industrial areas	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Residential & commercial development	Housing & urban areas	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Residential & commercial development	Tourism & recreation areas	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion

Purpose	Primary form used	Life stage used	Source	Scale	Level	Timing
Food - human	-	-			non-trivial	recent
Handicrafts, jewellery, etc.	-	-			non-trivial	recent
Pets/display animals, horticulture	-	-		international	non-trivial	recent

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Recommended citation
BirdLife International (2023) Species factsheet: Gorsachius goisagi. Downloaded from http://datazone.birdlife.org/species/factsheet/japanese-night-heron-gorsachius-goisagi on 11/12/2023.
Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://datazone.birdlife.org on 11/12/2023.