• 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
-	D	D1

Red List history

Year	Category	Criteria
2023	Endangered	D
2016	Near Threatened	B1ab(ii,iii);C1
2012	Near Threatened	B1ab(ii,iii);C1
2008	Near Threatened	C1
2004	Near Threatened
2002	Near Threatened
2000	Not Recognised
1994	Not Recognised
1988	Not Recognised

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	1,700 km2	medium
Area of Occupancy (breeding/resident)	1,408 km2
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	150-370, 150-180 mature individuals	medium	estimated	2022
Population trend	unknown	poor	-	-
Generation length	8.07 years	-	-	-
Number of subpopulations	1-5,1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: In 2021, this species had a range that encompassed only 915 km² of forest (per Hansen et al. 2013, Global Forest Watch 2022). Ferguson-Lees and Christie (2001) suggested that S. cheela typically occurs at densities/occupancy as sparse as one pair/100 km², although this is patently not appropriate for this species given the frequency and spread of data (eBird 2022). Instead, a much higher density of one pair/5-6 km² (as also suggested by Ferguson-Lees and Christie [2001] for some Spilornis populations) would give a population size of c.305-370 mature individuals. More recently, Manchi et al. (2021) estimated the density of S. elgini (with which this species is sometimes considered conspecific) to be 4-5 birds/25 km² (=0.16-0.2 birds/km²). This density estimate is considered the most reliable, since S. elgini is sympatric (and thus in competition with) S. cheela, which also applies to the present species. Notably, Manchi et al. (2021) found densities of 7-8 individuals/km² of S. cheela on the Andamans, suggesting that in these circumstances, the possible density of Spilornis species varies little. If the density recorded of S. elgini is true of S. klossi, the species would number only 150-180 mature individuals. Such a low number is broadly congruent with the (perhaps pessimistic) species-specific assessment of Ferguson-Lees and Christie (2001), who wrote of S. klossi that a 'high density would be necessary for [the] population to reach three figures'. There is little reason to suspect that the population density is especially high, with Rasmussen and Anderton (2012) noting that it is 'apparently scarce' and eBird (2022) data suggesting its encounter rate is broadly similar to that of S. elgini. Evaluating the available data, there is high confidence in the fact that this species' population size is likely to be small and this is confirmed by people familiar with the species, who describe it as 'decidedly rare' in the southern half of Great Nicobar and suggest its density may even be lower than that of S. elgini (Praveen J in litt. 2023). The population size is here estimated to be 150-370 mature individuals, with a best estimate of 150-180 (following the data from S. elgini as outlined above).

Trend justification: The only identified threat to this species is habitat loss and degradation. In the three generations (c.24 years; Bird et al. 2020) to 2022, forest loss in this species' range was equivalent to c.4% (using data between 2000 and 2020 and extrapolating) (per Global Forest Watch 2022, based on data from Hansen et al. [2013] and methods disclosed therein). The habitat requirements of this species are improperly known, but it is assumed to be at least somewhat forest dependent (Ferguson-Lees and Christie 2001; Rasmussen and Anderton 2005, 2012). However, most of the losses documented are from Great Nicobar Island, where according to satellite imagery (Google Earth 2022) clearance appears to be small-scale and undertaken by freeholders. Given the adaptability of other Spilornis (see summaries in Ferguson-Lees and Christie 2001, Billerman et al. 2022), it is entirely possible that this scale of habitat degradation does not negatively impact the species, and may even benefit it. Consequently, the population trend is set to unknown.

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

Country/Territory	IBA Name

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Subtropical/Tropical Moist Lowland	major	resident
Altitude	0 - 640 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Small-holder farming	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Unknown		Unknown
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Unknown		Unknown
		Stresses Ecosystem degradation
Residential & commercial development	Housing & urban areas	Timing		Scope		Severity		Impact
		Future		Minority (<50%)		Slow, Significant Declines		Low Impact: 3
		Stresses Ecosystem degradation, Ecosystem conversion
Residential & commercial development	Tourism & recreation areas	Timing		Scope		Severity		Impact
		Future		Minority (<50%)		Unknown		Unknown
		Stresses Ecosystem degradation, Ecosystem conversion

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Recommended citation
BirdLife International (2024) Species factsheet: Great Nicobar Serpent-eagle Spilornis klossi. Downloaded from https://datazone.birdlife.org/species/factsheet/great-nicobar-serpent-eagle-spilornis-klossi on 27/11/2024.
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 27/11/2024.