• 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
-	-	A2bcd+3bcd+4bcd

Red List history

Year	Category	Criteria
2020	Vulnerable	A2bcd+3bcd+4bcd
2016	Near Threatened	A3c
2012	Near Threatened	A3c
2009	Least Concern
2008	Least Concern
2004	Least Concern
2000	Lower Risk/Least Concern
1994	Lower Risk/Least Concern
1988	Lower Risk/Least Concern

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)	9,330,000 km2
Extent of Occurrence (non-breeding)	9,890,000 km2
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	20000-70000 mature individuals	poor	estimated	2009
Population trend	decreasing	-	estimated	2001-2024
Rate of change over the past 10 years/3 generations (longer of the two periods)	30-49%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	30-49%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	30-49%	-	-	-
Generation length	7.8 years	-	-	-

Population justification: A previous Asian Waterbird Census' observed 5,733 birds during 1987-1992, 5,558 during 1993-1997, 9,963 during 1998-2002, and 7,578 during 2003-2007 across some Indian and Pakistan sites (Li et al. 2009). Further surveys for the 2008-2015 period then observed across all of Asia and Australasia found an overall 29,577 birds across Myanmar (39 birds), Thailand (2), Bangladesh (74), India (17,776), Nepal (31), Pakistan (11,485) and Cambodia (170) (Mundkur et al. 2017). Under-counting is however thought to have been a major factor. Populations in the Southeast Asian part of its range are however very small and at higher risk of extinction (F. Goes in litt. 2020). In the whole Mekong basin for example, the population is currently estimated at less than 100 birds (F. Goes in litt. 2020). Using the best available information therefore, the population is thought to number at least 29,500 individuals, with the potential to reach a maximum of 100,000 individuals, assuming some surveys may be under-counted. Using a rounded population size of 30,000-100,000 individuals therefore, the population is placed in the band of 20,000-70,000 mature individuals.

Trend justification: Precipitous declines have occurred in parts of South-East Asia, whilst local increases and stability have been noted in a few areas of India, making the deciphering of past population trends difficult. Recent estimates in India show that the long-term trend of the species amounts to 41.2% decline (measured as an index of abundance in 2014/2015 relative to pre-2000 data; State of India's Birds 2020). An average annual change estimated at 5.2% (measured between 2014/2015 and 2018/2019; State of India's Birds 2020), additionally translates to over 70% decline over a 3-generation period (23.4 years; Bird et al. 2020). In China however, following historical declines, the species seems to be in recovery on at least one main site, although this is recognised as being only a small proportion of the species's overall range (W. Cheng in litt. 2020). Declines may however still be present on some riverine habitats, with certain sites known to be deteriorating and under continuous population decline (X. Zheng in litt. 2020). In Cambodia, the species is experiencing a continuing decline, with >80% reduction observed in the past 20 years (Claassen 2018, J. C. Eames in litt. 2020). It was also recorded to have undergone a strong decline during surveys in 2017-2019 at Ayeyarwady River between Myitkyina and Bagan, Myanmar (Zöckler 2020). Similarly on a tributary in the Chindwin River, a 90% decline had been observed since 2004 (C. Zöckler in litt. 2020). Reports to the International Waterbird Census (IWC) have been declining in the last decades, with an all-time maximum of 10,011 individuals in 2001, to 5,999 in 2010 and 3,944 in 2016 (IWC 2020, T. Mundkur in litt. 2020). This equates to a 76.6% decline over a 3-generation period, assuming the population had undergone an exponential decline since at least 2001.

However, based on recognition that previous methodologies in observing population trends for sandbank, riverine species as unreliable, primarily due to surveys being undertaken only in smaller wetlands (unrepresentative of larger areas), only in wintering seasons (excluding numbers at breeding sites), with large variability in coverage, and biased monitoring (S. Subramanya in litt. 2020, G. Sundar in litt. 2020, S. Quader in litt. 2020, S. Chowdhury in litt. 2020, Praveen. J in litt. 2020), the overall decline of the species is thought to be not as exaggerated as previously considered. The overall population also remains widespread and large (G. Sundar in litt. 2020). Nonetheless, precautionarily assuming that the species is declining across some sites in India (of which holds core breeding colonies and has undergone a long-term decline exceeding 40% per State of India's Birds [2020]), as well as declines in other peripheral sites across Myanmar, Cambodia, China, Nepal, and Bangladesh (A. Claassen in litt. 2020), it is considered that the population is undergoing an estimated rapid decline of 30-49% over a 3-generation period. The species is also expected to undergo a reduction over the next 3 generations, as threats, such as dam construction and disturbance of breeding sites, and predation, increase in prevalence.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Afghanistan	extant	vagrant			yes
Bangladesh	extant	native	yes
Bhutan	extant	native			yes
Cambodia	extant	native	yes
China (mainland)	extant	native	yes
India	extant	native	yes
Iran, Islamic Republic of	extant	vagrant			yes
Laos	extant	native			yes
Myanmar	extant	native	yes
Nepal	extant	native			yes
Pakistan	extant	native	yes
Thailand	extant	native	yes
Vietnam	extant	native			yes

Country/Territory	IBA Name
Pakistan	Indus Dolphin Reserve and Kandhkot wetlands

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Marine Intertidal	Mud Flats and Salt Flats	suitable	non-breeding
Marine Neritic	Estuaries	suitable	non-breeding
Wetlands (inland)	Permanent Freshwater Lakes (over 8ha)	major	resident
Wetlands (inland)	Permanent Rivers/Streams/Creeks (includes waterfalls)	major	resident
Altitude	0 - 600 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Livestock farming & ranching - Scale Unknown/Unrecorded	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Marine & freshwater aquaculture - Industrial aquaculture	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Ecosystem degradation
Biological resource use	Hunting & trapping terrestrial animals - Intentional use (species is the target)	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Reduced reproductive success, Species mortality
Climate change & severe weather	Storms & flooding	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species disturbance, Ecosystem degradation
Energy production & mining	Mining & quarrying	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Ecosystem degradation, Reduced reproductive success
Human intrusions & disturbance	Work & other activities	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species disturbance, Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Aquila fasciata	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Bandicota bengalensis	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Bubalus bubalis	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Canis familiaris	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Corvus splendens	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Mimosa pigra	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Threskiornis melanocephalus	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Varanus salvator	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Problematic native species/diseases	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Reduced reproductive success, Species mortality
Natural system modifications	Dams & water management/use - Large dams	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Rapid Declines		Medium Impact: 6
		Stresses Species disturbance, Ecosystem degradation, Ecosystem conversion, Reduced reproductive success
Residential & commercial development	Commercial & industrial areas	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Ecosystem degradation
Transportation & service corridors	Shipping lanes	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Slow, Significant Declines		Unknown
		Stresses Species disturbance, Ecosystem degradation

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Recommended citation
BirdLife International (2024) Species factsheet: River Tern Sterna aurantia. Downloaded from https://datazone.birdlife.org/species/factsheet/river-tern-sterna-aurantia on 23/12/2024.
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 23/12/2024.