Tanimbar Boobook (Ninox forbesi) - BirdLife species factsheet

Tanimbar Boobook Ninox forbesi

Current view: Data table and detailed info

Taxonomy

Taxonomic note

Ninox squamipila, N. hypogramma, N. hantu and N. forbesi (del Hoyo and Collar 2014) were previously lumped as N. squamipila following Norman et al. (1998), and before then were also lumped with N. natalis as N. squamipila following Sibley and Monroe (1990, 1993).

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.

IUCN Red List criteria met and history

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	-	-

Red List history

Year	Category	Criteria
2023	Least Concern
2016	Least Concern
2014	Least Concern
2012	Not Recognised
2008	Not Recognised
2004	Not Recognised
2000	Not Recognised
1994	Not Recognised
1988	Not Recognised

Species attributes

Migratory status	not a migrant	Forest dependency	medium
Land-mass type		Average mass	-

Range

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	9,500 km²
Area of Occupancy (breeding/resident)	5,200 km²
Severely fragmented?	no	-

Population

	Estimate	Data quality	Derivation	Year of estimate
Population size	12000-48000 mature individuals	poor	inferred	2022
Population trend	stable	-	suspected	-
Generation length	5.2 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: The population size of this species has not previously been quantified, although it is described as fairly common (Coates and Bishop 1997; Eaton et al. 2016, 2021). Within this species' range, c.3,000 km²of forest remains (Global Forest Watch 2022, based on data from Hansen et al. [2013] and methods disclosed therein). Densities of congeners range widely. Based on territory size data, Jakosalem et al. (2013) thought N. rumseyi could occur at densities of up to 20 mature individuals/km², but for the similarly sized N. boobook, Olsen et al. (2011) found territory sizes up to 10 times bigger. It is likely that N. forbesi occurs at densities closer to the former, with reports of four pairs recorded from a single point, including two within 100 m of one another in 2022 (J. Eaton in litt. 2023). Assuming an approximate density of 8-20 mature individuals/km², and that 50-80% of suitable habitat is occupied, the population is inferred to number 12,000-48,000 mature individuals.

Trend justification: Data on population trends for this species are lacking. Although forest cover loss is ongoing (Global Forest Watch 2022, based on data from Hansen et al. [2013] and methods disclosed therein) at a rate of c.5% over the past three generations (15.6 years: 2006-2022), most losses have been along roads, and this species is noted as being very tolerant of degraded forest, even that with cleared undergrowth (J. Eaton in litt. 2023). In the absence of other threats, the population is suspected to be stable.

Country/territory distribution

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

Important Bird and Biodiversity Areas (IBA)

Country/Territory	IBA Name

Habitats & altitude

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Artificial/Terrestrial	Subtropical/Tropical Heavily Degraded Former Forest	suitable	resident
Forest	Subtropical/Tropical Moist Lowland	major	resident
Altitude	0 - 320 m	Occasional altitudinal limits

Threats & impact

Threat (level 1)

Threat (level 2)

Impact and Stresses

Biological resource use

Logging & wood harvesting - Unintentional effects: (large scale) [harvest]

Timing

Scope

Severity

Impact

Ongoing

Minority (<50%)

No decline

Low Impact: 4

Stresses
Ecosystem degradation, Ecosystem conversion