Archived 2020 topic: River Tern (Sterna aurantia): revise global status?

BirdLife species factsheet for River Tern

River Tern (Sterna aurantia) breeds on sandbars and islands along large rivers and reservoirs across south and south-east Asia. The global population is estimated at 50,000-100,000 individuals (Wetlands International 2012), which roughly equates to 30,000-70,000 mature individuals. River Tern is facing a multitude of threats: its nesting areas are susceptible to flooding and cyclones (del Hoyo et al. 1996, Debata 2019). Eggs and chicks are predated by terrestrial animals and avian predators (Mundkur 1991, Siddiqui et al. 2007, Reshamwala 2017), or are caught in abandoned fish nets (Narwade and Fartade 2013).  

The species is currently listed as Near Threatened under Criterion A3c (BirdLife International 2020), due to an expected moderate decline driven by increasing human disturbance, sand mining and dam projects over the following three generations. Alongside other species breeding in riverine habitats across Asia, such as Indian Skimmer (Rynchops albicollis), there is concern that the rate of population reduction has been greater than previously suspected and that the species is now declining at a rapid rate. Declines have been reported across much of the range, including predicted imminent extinction in Cambodia (Claassen 2018) and reductions to small numbers in Myanmar (Zöckler 2019, A. Claassen in litt. 2020), Bangladesh (Chowdhury 2014) and China (Dasgupta 2019). As such, the species may warrant listing at a higher threat category, and is therefore reassessed here against all Red List Criteria.

Criterion A – The species, in common with other sandbar nesting riverine species in Asia, is undergoing rapid declines. In Cambodia, the population has declined by more than 80% in the past 20 years to a population estimated at just 54-62 individuals (Claassen 2018). In Myanmar, only a single pair was recorded along the Ayeyarwady in recent years, in contrast to more than 60 little more than a decade ago (Zöckler 2019, C. Zöckler in litt. 2020). Further declines have been recorded in Thailand, Laos, China and Nepal (del Hoyo et al. 1996, Thewlis et al. 1998, W. Duckworth in litt. 2011, Yang Liu in litt. 2011, Inskipp et al. 2016, Dasgupta 2019).

Numbers reported to the International Waterbird Census (IWC) database declined from 10,011 individuals in 2001 to 5,999 individuals in 2010 and to 3,944 individuals in 2016 (T. Mundkur in litt. 2020). Assuming an exponential decline, this equates to a reduction of 76.6% over three generations (23.4 years; Bird et al. 2020)*. If we take observational records to the IWC database as a proxy of the population size, the population would be declining at a rate of 70-79% since at least 2001. If we further assume that population declines continue at a similar rate, River Tern may be listed as Endangered under Criterion A2bcd+3bcd+4bcd.

Criterion B – The Extent of Occurrence (EOO) is estimated at 9,730,000 km2. This does not approach the threshold for listing the species as threatened under Criterion B1. River Tern is therefore assessed as Least Concern under this criterion. The Area of Occupancy (AOO) has not been quantified according to IUCN Guidelines (see IUCN Standards and Petitions Committee 2019), and thus River Tern cannot be assessed against Criterion B2.

Criterion C – The species’s population size has been estimated at 50,000-100,000 individuals, roughly equivalent to 30,000-70,000 mature individuals.This does not approach the threshold for listing as threatened under Criterion C. River Tern is therefore assessed as Least Concern under this criterion.

Criterion D – The population size and range are too large to warrant a listing as threatened under Criterion D, and thus River Tern is considered Least Concern under this criterion.

Criterion E – To the best of our knowledge no quantitative assessment of the probability of extinction has been conducted for this species, and so it cannot be assessed against this criterion.

Based on the above assessment, it is proposed to list River Tern (Sterna aurantia) as Endangered under Criterion A2bcd+3bcd+4bcd. We welcome any comments on the proposed listing and specifically ask for information on the timeframe of declines: Data from IWC suggest a steady decline at a rate of 50-79% over three generations since at least 2001. Has the rate of decline increased gradually before that? Was the population stable or decreasing at <25% over three generations during 1988-1992? Have declines increased to 25-29% over three generations during 1992-1996, qualifying the species for listing as NT, and then increased to 30-49% over three generations during 1996-2000, qualifying for a listing as VU? Alternatively, has the rate of decline increased suddenly during the period 1996-2000, so that the species would have qualified for uplisting from NT straight to EN?

Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’ Red List status. Therefore, please make sure your comments are relevant to the species’ Red List status and the information requested. By submitting a comment, you confirm that you agree to the Comment Policy.

*Bird generation lengths are estimated using the methodology of Bird et al. (2020), as applied to parameter values updated for use in each IUCN Red List for birds reassessment cycle. Values used for the current assessment are available on request. We encourage people to contact us with additional or improved values for the following parameters; adult survival (true survival accounting for dispersal derived from an apparently stable population); mean age at first breeding; and maximum longevity (i.e. the biological maximum, hence values from captive individuals are acceptable).

An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.


Bird, J.P., Martin, R., Akçakaya, H.R., Gilroy, J., Burfield, I.J., Garnett, S., Symes, A., Taylor, J., Şekercioğlu, Ç.H. & Butchart, S.H. (2020). Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology, online first view.

BirdLife International. 2020. Species factsheet: Sterna aurantia. (Accessed 20 May 2020).

Chowdhury, S. U.; Foysal, M.; Sharpe, J.; Shahadat, O. 2014. A survey for Black-bellied Tern Sterna acuticauda and other riverine birds on the Jamuna and Padma rivers in Bangladesh. Forktail 30:84–89.

Claassen, A. H. 2018. Ten-year species action plan for the Cambodian population of River Tern Sterna aurantia, 2018-2028. Phnom Penh, Cambodia.

Dasgupta, S. 2019. Where did the birds go? Q&A with river tern researcher Bosco Chan. Mongabay. (Accessed 28 May 2020).

Debata, S. 2019. Impact of cyclone Fani on the breeding success of sandbar-nesting birds along the Mahanadi River in Odisha, India. Journal of Threatened Taxa 11(14): 14895–14898.

del Hoyo, J., Elliott, A., and Sargatal, J. 1996. Handbook of the Birds of the World, vol. 3: Hoatzin to Auks. Lynx Edicions, Barcelona, Spain.

Inskipp, C.; Baral, H. S.; Phuyal, S.; Bhatt, T. R.; Khatiwada, M.; Inskipp, T.; Khatiwada, A.; Gurung, S.; Singh, P. B.; Murray, L.; Poudyal, L.; Amin, R. 2016. The Status of Nepal’s Birds: the National Red List series. Zoological Society of London.

Mundkur, T. 1991. Nesting and feeding ecology of aquatic birds in Saurashtra and Gulf of Kachchh. Ph.D. Thesis, Saurashtra University, India.

Narwade, S.; Fartade, K. 2013. Breeding colony of River Tern on manmade construction in the Deccan Plateau, Maharashtra. Mistnet 14: 18-19.

Reshamwala, S. 2017. River Terns of Bhadra. JLR Explore. (Accessed 28 May 2020).

Thewlis, R. M.; Timmins, R. J.; Evans, T. D.; Duckworth, J. W. 1998. The conservation status of birds in Laos, 8 (supplement). Bird Conservation International.

Wetlands International. 2012. Waterbird Population Estimates. (Accessed 20 May 2020).

Zöckler, C. 2019. Winter bird monitoring at the Ayeyarwady River, Myitkyina – Bagan, Myanmar 2017, 2018 and 2019. Report to Manfred-Hermsen Stiftung and Fauna and Flora International.

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22 Responses to Archived 2020 topic: River Tern (Sterna aurantia): revise global status?

  1. Xi ZHENG says:

    River Tern was once described as common in western and southern Yunnan of China, along the Xishuangbanna section of the Mekong, the Ruili River (Shweli River in Myanmar) and Dayingjiang River of the Irrawaddy drainage basin in Dehong (Yang et al. 1995).

    However, Dayingjiang River of western Yunnan is currently the only known River Tern breeding site in China. Outside Dayingjiang, singles have been seen in recent years along the Brahmaputra in the Medog region of southeastern Tibet border Arunachal Pradesh of India. The riverine habitat where River Terns occur has been deteriorating, and continuous population decline has been noted in the last few years, as elsewhere in the region. The breeding population along the Dayingjiang River declined from 13 individuals in 2014 to seven in 2017, and only five birds were recorded in 2018.

    Kadoorie Farm and Botanic Garden (KFBG), together with local forestry department and other partners, launched a River Tern conservation programme in 2019. Seven individuals were found during systematic field survey. With concerted efforts from the joint conservation team, 6 juveniles successfully fledged and increased the Chinese population to 13 individuals. Unfortunately, only 5 individuals returned to the breeding site in 2020. With 3 juveniles fledged and 3 chicks hatched till 3 June, the total population is 11 individuals.

  2. The assessment of status should not be made based on data obtained from small wetlands. Sandbars and exposed sandy islands in large reservoirs are a major and potential habitat for the species. Unfortunately, such large wetlands are hardly ever surveyed properly. For example, a recent survey of birds at Almatti Backwaters in Bagalkot, Karnataka, (data not published yet) revealed the presence of over 11,000 nests of the species spread over some 12 exposed sandy islands (e.g., see for data on one of the smaller islands). River Terns breed at Almatti Reservoir when lowering water levels during summer starts to expose raised sandy islands. If concerted efforts are made to assess the population in all the large reservoirs, it may show a different status for the species. Unfortunately, waterfowl surveys have not focussed on surveying summer breeding colonies in large wetlands. The references listed does not reflect breeding colony surveys. Also, IWC data is being collected, when the species in not breeding.

    Thus, the present assessment of its status as Endangered, is being made too early and also in great haste. For e.g., I would consider the species to be Near Threatened in Karnataka, India.

    • Dr. Christoph Zöckler says:

      Dear Dr. Subramanya,

      Thank you for your impressive account from the Almatti reservoir, an area I am not familiar with. 11,000 pairs sounds almost unbelievable and too good to be true. Do you think that there are many similar places nearby or elsewhere in India that have not been surveyed properly?
      Also do you have records from previous years or did surveys only started this year. I noticed you visited the site earlier in March according to your ebird data but you only noticed 10 River Terns. They should have been on nests by then as well? Maybe you surveyed only a small part?
      I also noticed that none or hardly any of the birds in your photos are actually nesting. I also don’t see young birds on the photos you provided which would be likely for this time of the year, considering that they start nesting in Myanmar at similar latitudes in early February. I am sure that with so many birds involved there must be nests, but it would be good and quite important to reveal the real number of nesting pairs as not all birds seem to be engaged in nesting. In any case it is an impressive site and as far as I know the most important site for the species so far. Also, it would be good to learn more about the threats to the ground nesting birds at this site. Are there straying dogs or other ground predators of any significance, local people collecting eggs or other disturbances? Are the water tables relatively stable? Any hunting or trapping or bait poisoning activities going on , not necessarily targeting the terns but waterfowl and terns are accidently killed too?
      Thank you for your fascinating report and I am keen to learn more about this site

    • Gopi Sundar says:

      I quite agree with Dr. Subramanya on two things.

      One, winter censuses are potentially not ideal to count this species since the birds spread out quite a bit in that season, and uses inland wetlands and rivers the majority of which are not visited for such censuses.

      Two, breeding concentrations in large reservoirs, even a few large rivers, are pretty impressive. Karnataka alone would have at least half a dozen or so of very large breeding colonies in rivers and reservoirs that have nests in the high hundreds if not low thousands.

      Though not as massive, breeding concentrations in north and central India are fairly widespread in both natural and artificial wetlands that are largeish. Add to this the large numbers of smaller colonies that breed in smaller river islands, and in very small islands formed in medium-sized wetlands across the wetter portions of south Asia, the breeding population is very fortunately still quite large.

      Like some other ornithologists and concerned folks in south Asia, I am not for publicly announcing locations with large concentrations of breeding terns. The problem of enthusiastic photographers and “volunteer conservationists” has increased to a very high level in many countries, and India has not been spared this problem.

      There does not seem to be adequate information at this time to upgrade the conservation status of River Terns at this time.

      However, the situation in south-east Asia is quite dire for most riverine bird species including the River Tern. There ought to be a way to highlight such imperiled populations for species that otherwise have large populations elsewhere in their distribution range. A major part of disagreements for many species stems for their greatly threatened status in south-east Asia which is contrasted with high population levels in south Asia.

      Gopi Sundar.

  3. In Nepal, River Tern is a rare and very local visitor which has been assessed as Critically Endangered (Inskipp et al., 2016). Its population has sharply declined since the early 1990s and now the population size is very small. The distributional range of the species has also reduced since the early 1990s; now River Tern is mainly recorded from two protected area Bardia National Park and Koshi Tappu Wildlife reserve. It is severely threatened by food shortage (illegal fishing in protected areas and over-fishing outside the protected areas’ system), destruction of its breeding habitats on rivers, disturbance and hunting.

  4. Dear Dr. Zöckler,

    I visited a number of locations along the vast backwater areas on foot during March and the checklist that you are referring to, came from one such locations along the backwater. River Terns do not nest along the shoreline, where the land has recently been exposed by receding waters and are prone to human disturbance. The main nesting area that I refer to, is found inside the reservoir and these are exposed islands, insulated by water all around. The eBird checklist link that I have given is again that of an island colony in an another part of the reservoir.

    The Large reservoirs and their backwaters in India are hardly or less properly surveyed. Most of these large waterbodies are monsoon fed (June – October). Due to continuous release of water from these irrigation project reservoirs, by summer, receding waters will expose a number of sandbars and raised sandy islands. Since water forms an insulating barrier against ground predators, birds like terns, resident provers and pratincoles gather around to nest on these islands, more or less synchronously. The 2019 monsoon got extended by a month with wide-ranging floods in northern Karnataka and as a consequence, the nesting of terns was also pushed by about a month. We used a motorboat to survey birds, as these nesting areas are not accessible by foot. We GPS tracked our route and collected time-segmented samples of all birds seen from a safe distance. These counts were also augmented by a large number of location tagged images to work up the final counts. Almatti Reservoir is one of our large reservoirs and is designed for a flood intensity of about 10,95,000 Cusecs with a total submergence area of 48787 ha. There are a number of such reservoirs in other parts of Karnataka/India with their own bird populations. Proper coverages of such reservoirs and their backwaters is not being done to a large extent. Thus, there is a need for a concerted effort with suitable methodology to assess waterbird populations in such large reservoirs.

    Most of the birds we observed on the islands were seen nesting synchronously and were more or less incubating. We did record young ones, but in very low numbers, as our survey was quite early in the delayed nesting season this year. The details that I have provided is only from this year and we hope to make these surveys a yearly feature.

    Birdwatching in India has been more city-centric and wetlands in rural and remote areas are not adequately covered. Also, in recent years, most of the wetlands in and around the cities are being developed and the development model is not biodiversity friendly. There is a drastic decline in bird numbers in these altered wetlands, as compared to the 1980-90s. Given such a situation, I feel that these large reservoirs with their extensive backwaters are going to be important refuges for large congregation of waterbirds. Proper counts made at these large waterbodies need to be considered before making decisions on the status of waterbirds. Thus, up-listing River Tern as Endangered, to me, does not seem right, without properly assessing the prevailing ground situations in large waterbodies and due to lack of surveys during breeding season.

    I am happy that you bring up the issue of threats. The water levels are not stable and we feel that, as you rightly point out, with lowering water levels, these sandy islets may become accessible to stray dogs and we perceive it to be a serious threat. The staff from the local Wildlife Department, who were part of the survey, were not aware of any egg collection or bird trapping by locals living around these backwaters. Besides these, with publicity, photographers, as Dr. Sunder points out, are emerging as a serious source of disturbance in bird areas and it is time that we recognize them as a threat. Plans are afoot to get the Almatti area declared as a Conservation Reserve to provide much needed protection to these bird congregations.

  5. I’m writing bring in whatever information can be added from the recently published State of India’s Birds (SoIB) 2020 report (, in which birdwatchers’ lists uploaded to eBird were used to estimate long-term (c.25y) and current (5y) trends in an index of abundance (the frequency of reporting), and to estimate range size (Area of Occupancy: AOO) for a large number of species. All estimates are for India only.

    In the excel file downloadable on the website you’ll see that the decline in the index of abundance over c.25 years is about 40%, and the current annual change in this index is about -5% per year. (Of course this is an index only, and isn’t population size itself.) The 40% decline isn’t as large as in southeast Asia (according to the factsheet), but under criterion A2b would warrant an uplisting to VU. If we take current decline, and assume it remains constant, then the population change projected in three generations (c.23y) is -70%, which would put it in EN.

    It’s worth discussing to what degree the sorts of biases in visits/counts described by Drs S. Subramanya and Gopi Sundar, above might influence these estimates. Here are two possible reasons that the declines estimated by SoIB might be spurious:
    1. Birdwatchers used to visit large reservoirs much more in the past than currently, and that trends continues.
    2. The major sites are largely unsurveyed by birdwatchers — River Terns are doing fine there, but declining in other habitats.

    It’s worth pointing out that the trends in SoIB are averaged across all seasons, so don’t reflect only breeding or only non-breeding seasons.

    With all this in mind, it seems likely that there has indeed been a decline, even though population numbers are still fairly large.

  6. Dr Anwaruddin Choudhury says:

    In 1980s and 1990s one was unlikely to miss River Terns across NE India, more particularly Assam. Every wetland including ox-bow lakes, sluggish channels and large and small rivers, it was a common sight. On the sandy islets and tracts of the Brahmaputra, Subansiri, Lohit and Dibang they used to rest in large gatherings and in summer there used to be nests. Although there is no deliberate hunting, the number of birds declined sharply. The nesting sites have now fishermen’s camps. The population decline is too conspicuous. However, as reported by Dr. Subramanya of the status in Karnataka, I think it could be upgraded to Vulnerable.

  7. I agree with others that the decline of the River Tern is not as dire as described here. In Bangladesh, there are several recent sightings of River Tern (nests, as well as juvelines) from Padma river in Rajshahi Division where local birdwatchers are more active now. Moreover, the breeding population (c.10-20 pairs) in the coast of Bangladesh still remains more or less the same in the last decade.

    The IWC/AWC maximum counts included 5,733 individuals in 1987-92; 5,558 in 1993-97; 9,963 in 1998-02; 7,578 in 2003-07 (see page no 50 in Li et al. 2009); 5,983 in 2008-12 and 5,070 in 2013-2015 (see page no 50 Mundkur et al. 2017). This doesn’t strike me as a sharp decline, I rather see a fluctuation, possibly because of different survey efforts in different years.

    Nevertheless, all published accounts do indicate that there has been a steady decline especially in southeast Asia, hence I would also vote to uplist it to Vulnerable.


    Li, Z. W. D., Bloem, A., Delany, S., Martakis, G. and Quintero, J. O. (2009) Status of waterbirds in Asia – results of the Asian waterbird census: 1987-2007. Kuala Lumpur, Malaysia: Wetlands International. [PDF here –

    Mundkur, T., Langendoen, T., & Watkins, D. (2017). The Asian Waterbird Census 2008–2015-Results of Coordinated Counts in Asia and Australasia. Wetlands International, Ede, 144pp. [PDF here –

  8. Dr. Christoph Zöckler says:

    It is very interesting to see all the different comments from India, the core breeding range of the species, which to my mind provides a different picture in different parts of the country. Thank you Dr. Subramanya for providing further details on the stable situation in Bagalkot. While in Karnataka the situation is much better than generally thought, the situation in other more marginal areas seem to be much worse and the reason for concern.

    Maybe I add some information from Myanmar at this point, where I have been working over the past 12 years. I surveyed some 500 km of Ayeyarwady River over three years in winter and early breeding season. Here I found only one pair of nesting River Terns in each year 2017, 2018 and 2019. Davies et al. (2004) and also Thet Zaw Naing and van der Ven reported much higher figures of up to 80 birds on a river stretch I did not find any. Like Dr Choudhury from NE India listed, I also observed many breeding habitats on the river occupied by fishing camps, converted into small farms, turned over by gold mining and subjected to sand and pebble abstraction. Similar declines were reported from the right tributary Chindwin where van der Ven (2004) counted 391 but recent surveys only revealed 40-50 (Naing Lin of WCS pers. comm.) which relates to almost 90% decline. These developments on the margins , also reported from Nepal, Thailand and Cambodia are concerning.

    I agree with Dr Choudhury that considering the favourable condition in several parts of India as reported from Karnataka, but the widespread decline from many areas on the eastern and northern edge of the distribution an uplisting to VU might be justified. I also highly recommend to monitor the situation across the range and revisit the red-list status in a year’s time and use the period for more in depth surveys of breeding colonies but also threats. I am for example concerned about the plans to convert the Ayeyawady into a water transport route, dredging on the Chindwin River for commercial and passenger transport and many other small scale threats. Maybe, the sum of all these threats in its totality are just too much for most of the remaining nesting colonies. I hope this discussion will also trigger more urgency and we can also accelerate our conservation efforts and focus on the riverine bird communities.

  9. Simon Mahood says:

    Less than 50 pairs in Cambodia. Rapid decline ongoing but too few birds relative to the population in India to impact the global threat assessment.

  10. Praveen J says:

    May I caution the way this particular dataset is getting interpreted ?

    “Numbers reported to the International Waterbird Census (IWC) database declined from 10,011 individuals in 2001 to 5,999 individuals in 2010 and to 3,944 individuals in 2016 (T. Mundkur in litt. 2020). Assuming an exponential decline, this equates to a reduction of 76.6% over three generations (23.4 years; Bird et al. 2020)*. If we take observational records to the IWC database as a proxy of the population size, the population would be declining at a rate of 70-79% since at least 2001. If we further assume that population declines continue at a similar rate, River Tern may be listed as Endangered under Criterion A2bcd+3bcd+4bcd.”

    There is a large variability in the wetland coverage of IWC – year on year – and the decline should be atleast calculated amongst a set of regularly monitored wetlands. For e.g. lack of coverage of an inland reservoir in Karnataka in a few years would give the same decline values. Hence, can there be deeper analysis on this dataset – possibly using a proxy species as well?

  11. The situation with River Terns in Cambodia, Myanmar, China, Nepal and Bangladesh is dire and those populations need to be considered critically endangered at national levels. However, those countries are really peripheral to the global population, the bulk of which is in India. Any decision to uplist the global status to vulnerable or endangered should be based on the River Tern’s situation in India, and not rely overly much on the information coming in from those of us working in peripheral range countries. I am grateful to the Indian researchers who have provided information to this forum, and I sincerely hope that more work is done in India to get a better idea of the population status there.

  12. Ramesh Chaudhary says:

    Sighting of River Tern has declined sharply after 1990. It has been categorized as rare and local visitor (Inskipp et al., 2016). There has been only few recent records from Koshi Tappu Wildlife Reserve and Bardia National Park. I think, its conservation status should remain as Critically Endangered.

  13. Roberts (1997) considered this species a common resident throughout the Indus plains being virtually absent from Balochistan and Khyber Pakhtunkhwa.
    I conducted an online survey. The birdwatchers’ statistics are as follows;
    Birdwatching area
    Status of the species
    Any breeding observed
    Any decline observed
    Threats noted
    Population status
    1) Sindh-Langh lake, Larkana
    Very Common
    2) Sindh- Khairpur wetlands
    Very Common
    3) Sindh- Haleji lake
    4) Sindh_ Bhambore wetlands
    Stable, species rarely enter sea creeks and delta.
    3) Punjab- Multan wetlands
    Very common, flocks up to hundreds are a common sight
    4)Punjab- Sadiqabad
    5) Punjab- Rahim Yar Khan
    Year round visitor
    6) Punjab- Head Marala
    Yes, around 20 percent
    Not known
    7) Punjab- Head Baloki
    Yes, around 40-50 percent
    Habitat destruction; Water bodies converted to cultivation fields. Pollution.
    8) Capital city -Rawal dam
    9) Gilgit Baltistan
    wetlands throughout provinces
    No records, not a high altitude species

    It can be concluded that the species has had selective decline in a few particular areas. Other than those regions, the species is common throughout small and large wetlands across Pakistan.
    It is to be noted that many birdwatchers when asked about the decline of the species showed signs of ‘laughter’ about this very common species. The species is doing well in most of the regions throughout Pakistan.
    It must also be noted that the reason for many birdwatching sites having no breeding signs is the lack of will by birdwatchers. Many birdwatchers did not target the species for its breeding sites in their ‘birding spots’.
    Some birdwatcher’s mentioned that the spread of irrigation canals and fish ponds have led to a much greater dispersal of this species and therefore, an increase in population of this species across Pakistan. It was also noted by me in and around small wetland patches in Southern Sindh.

  14. Praveen J says:

    Trends from State of India’s birds available in the link above. Caveats to interpret them were posted by Suhel Quader earlier.

  15. Red List Team (BirdLife International) says:

    Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. The window for consultation is now closed. We will analyse and interpret the new information and post a preliminary decision on this species’s Red List status on this page in early July.

    Thank you once again,
    BirdLife Red List Team

  16. Red List Team (BirdLife International) says:

    Preliminary proposal

    The following decision has been informed based on the acknowledged uncertainty in survey methods used to provide the core information in the initial forum topic. However, as per guidance provided by the State of India’s Birds (2020) indicating significant declines persisting within the species’s Indian range, the overall population is nevertheless considered to be undergoing declines exceeding the required threshold for a threatened category.

    Thus, whilst also accounting for its widespread occurrence, our preliminary proposal for the 2020 Red List would be to list the River Tern as Vulnerable under Criterion A2bcd+3bcd+4bcd.

    There is now a period for further comments until the final deadline in mid-July, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from the initial proposal.

    The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021 (information on the IUCN Red List update process can be found here), following further checking of information relevant to the assessments by both BirdLife and IUCN.

  17. Red List Team (BirdLife International) says:

    Following closure of the forums, we have received a comment (via email) from a correspondent that confirms stability of the species across some sites in India. We do however note that this may not represent the overall population. We also received comments (via email) from two correspondents that the species is likely in recovery following conservation efforts in China; however, we note that this represents a small proportion of the overall population.

    • Red List Team (BirdLife International) says:

      The comment, submitted by S. Balachandran on 30th June depicting species status in India, is as follows:

      Status in Chilika Lake:
      The brackish Chilika lake (total area around 1100 sk km) located in India support around 1500 River Ten from the entire Lake. The Nalabana Island (a declared bird Sanctuary) located in the lake is the submergible islands emerges between November to April. BNHS has been monitoring since 2001.Every year during November to February 300-400 River tern frequent this island for feeding and night roosting. The numbers in the island started building up from mid February when the breeding activities start and reach up to 14000 during April. This species nest along with the Gull-billed Tern and Little Tern. In 2002 we have recorded 540 nests of River Tern along with Gull-billed Tern (326 nests) and Little tern (27nests). But when 20% of these nests fledged successfully the remaining eggs and chicks were washed away due to the submersion of the island during the first week caused by the ingression of seawater. It is a regular annual phenomenon. As the early breeders which make nests till mid March managed to fledge successfully, but majority of them were washed away. The breeding success was around 20%. The nest numbers for River tern started declining since 2003 and come down to around 200 in 2008, though not much changes happened in Gull-billed tern nest numbers. There after the numbers gone below 50 during 2010, and since 2011 River Tern abandoned this island completely for nesting, and the other species abandoned completely from 2012. But since 2013, 20 to 30 nests were observed in a small islet located 7 km away from Nalabana Sanctuary called Panchgudhi (unprotected) started nesting in January onwards and successfully fledged. When numbers increased up to 95, the fishermen started collecting the eggs and cook there itself to eat. There also 20-30% breeding success could be recorded till 2020.
      Despite all these issues, the numbers occurring on the Island is almost Stable during the non-breeding season. However, the increased numbers observed during March -April due to the arrival of nesting birds probably from other parts of the Lake and elsewhere are not observed.

      Status at Pong Dam:
      Pong Dam built during 1974 for Hydro-electric power generation and irrigation started attracting waterbirds in increasing numbers during the last two decades. This is a Ramsar site and Wildlife sanctuary. BNHS did intermittent bird monitoring through some research projects and some training programmes. Bird ringing and neck collaring, and satellite tracking studies were undertaken at this Dam. Two intensive breeding birds surveys were also carried out during 2006 and 2015 summer. Here also the River tern nests along with Gull-billed tern and Little Tern. In 2006 a total of 384 nests of River tern were observed. Of them 126 nests were observed in one island called Ranseer Island located two km from the shoreline of Nahrota-Surian. The remaining nests were located in the shoreline area of Nahrota-Surian. Here not much threats to these species except the cattle trampling.

      In 2015 June also we have recorded over 400 nests found along the Naharota Surian side and more in a new site Jagathpur (N 32° 02.243 E 076° 02.265). The Ranseer island the regular nesting site was not surveyed due to lack of boat service. Hence,the numbers would have been another 100. Almost every winter (non-breeding season) we used to observe between 800 and 1000 individuals at all over Pong Dam.

      Status Mahanadhi (Odisha):
      While undertaking nesting surveys and ringing of Indian Skimmer in 2016 April at the downstream of Mahanadhi in a sandbar near Mundali Dam 22 nests of River Tern nests were sighted along with The Indian Skimmer nests. In the subsequent winter survey along the Sand bars located between the upstream and downstream of Mahanadhi river System River terns were sighted in small blocks between 10 and 20 at seven sand-bars.
      Considering all these observations from our study sites based on our long-term observation it appears that the population is stable. By considering the current status in its stronghold in Karnataka river System as pointed by Dr Subramanya, it can be considered to keep under the Current Near-threatened category.

  18. Gopi Sundar says:

    Thanks to the team for ensuring that folks could contribute their individual bits of information and understanding towards a better understanding of the status assessment of the River Tern.

    It is not clear why the BirdLife team is taking the SoIB metric as an “advisory” for the species given that eBird data is one among the various incomplete and imperfect sets of observation being included in this discussion. As BirdLife folks have correctly indicated that some multi-year multi-site observations are from small portions of the species range, eBird information has to be considered similarly, as also other volunteer efforts such as the mid-winter waterbird counts. Putting all of these together in similar ways will be most useful for this process.

    Dr. Suhel has clearly provided the potential problems of SoIB metrics for River Terns. Praveen has also raised one potential problem of data from mid-winter waterfowl census. I sincerely doubt if we can take increased quantity of observations to mean improvement of quality of information for the various reasons that these folks, and others, have pointed out. Declines observed in large sets of volunteer contributions can be due to reasons unrelated to actual population changes.

    I ask that we continue the IUCN Red List process by taking into account any and all information that is provided in these forums. All of these individual bits will have their idiosyncrasies, but are common in being incomplete and imperfect. Biasing the species status assessment by regarding only one of these bits of incomplete and imperfect data as an “advisory” seems to defeat the purpose of these forums. Even if no other observations exists, trends from volunteer data sets are highly unlikely to be complete or without problems and should be treated with caution for the reasons that others have pointed out earlier in this forum (and other reasons).

    A large amount of information is always likely to remain with folks conducting field work. These forums remain a great way to incorporate observations of these researchers and enthusiasts as well into status assessments.

    Gopi Sundar.

  19. Red List Team (BirdLife International) says:

    Recommended categorisation to be put forward to IUCN

    The final categorisation for this species has not changed. River Tern is recommended to be listed as Vulnerable under Criterion A2bcd+3bcd+4bcd.

    Many thanks for everyone who contributed to the 2020 GTB Forum process. The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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