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

Taxonomic note
Locustella castanea (del Hoyo and Collar 2016) was previously lumped with L disturbans and L. musculus under the name Bradypterus castanea. Rheindt et al. (2020) set out further vocal and genetic data to support the split of Locustella castanea into three monotypic species: L. castanea, L. disturbans and L. musculus. Monotypic.

Taxonomic source(s)
Handbook of the Birds of the World and BirdLife International. 2022. Handbook of the Birds of the World and BirdLife International digital checklist of the birds of the world. Version 7. Available at: https://datazone.birdlife.org/userfiles/file/Species/Taxonomy/HBW-BirdLife_Checklist_v7_Dec22.zip.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	-	-

Red List history

Year	Category	Criteria
2022	Least Concern
2016	Not Recognised
2012	Not Recognised
2008	Not Recognised
2004	Not Recognised
2000	Not Recognised
1994	Not Recognised
1988	Not Recognised

Migratory status	not a migrant	Forest dependency	does not normally occur in forest
Land-mass type		Average mass	-

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	1,800 km2
Area of Occupancy (breeding/resident)	1,516 km2
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	14000-28000 mature individuals	poor	estimated	2022
Population trend	stable	-	suspected	-
Generation length	2.5 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: The population size of this species has not been formally estimated. It was described as uncommon by Eaton et al. (2021). Survey efforts in 1995?1996 and in 2011 generated few records of the species (Reeve et al. 2014) but inside forest in optimal habitat, pairs can be spaced only c.200 m apart (J. Eaton in litt. 2022). Assuming that this description translates to a density of c.50 mature individuals/km², and that c.20-40% of forest within its elevational range (totalling 1,400 km²) is occupied, the population is estimated here to number 14,000-28,000 mature individuals.

Trend justification: The population is suspected to be stable in the absence of evidence for any declines or substantial threats. Remote sensing data (Global Forest Watch 2022, using data from Hansen et al. [2013] and methods disclosed therein) indicate minimal (<1% over ten years) forest loss in this species' elevational range and it is also reported to be at least somewhat tolerant of degraded habitats, including grasslands (White and Bruce 1986, Coates and Bishop 1997).

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Indonesia	extant	native	yes

Country/Territory	IBA Name

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Subtropical/Tropical Moist Montane	major	resident
Altitude	1200 - 2430 m	Occasional altitudinal limits	(min) 750 m

Threat (level 1)	Threat (level 2)	Impact and Stresses
Biological resource use	Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		No decline		Low Impact: 4
		Stresses Ecosystem degradation, Ecosystem conversion

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Recommended citation
BirdLife International (2024) Species factsheet: Buru Grasshopper-warbler Locustella disturbans. Downloaded from https://datazone.birdlife.org/species/factsheet/buru-grasshopper-warbler-locustella-disturbans on 22/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 22/12/2024.