VU
River Tern Sterna aurantia



Taxonomy

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
- - 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
Species attributes

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

Estimate Data quality
Extent of Occurrence (breeding/resident) 9,330,000 km2
Extent of Occurrence (non-breeding) 9,890,000 km2
Severely fragmented? no -
Population
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 distribution
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

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Pakistan Indus Dolphin Reserve and Kandhkot wetlands

Habitats & altitude
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  

Threats & impact
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

Recommended citation
BirdLife International (2024) Species factsheet: River Tern Sterna aurantia. Downloaded from https://datazone.birdlife.org/species/factsheet/river-tern-sterna-aurantia on 03/12/2024.
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 03/12/2024.