Archived 2011-2012 topics: Black-bellied Tern (Sterna acuticauda): request for information

This discussion was first published on Dec 1 2010 as part of the 2010-2011 Red List update.

Initial deadline for comments: 31 January 2012.

Link to BirdLife factsheet for Black-bellied Tern

Black-bellied Tern Sterna acuticauda is listed as Near Threatened under criteria A2c; A3c; A4c, on the basis that it is inferred to be undergoing a continued decline of 20-29% over 27 years (estimate of three generations).

This decline is due to a number of threats including habitat destruction through conversion to agriculture, river flooding and flow impediment through damming, egg collecting, disturbance and depletion of food supplies through overfishing. The species is now considered probably extinct in Cambodia, with none recorded since the last breeding record in 2003 (Goes et al. 2010). River damming, disturbance, predation by dogs and egg collecting are highlighted as causes of the species’s disappearance from Cambodia (Goes et al. 2010). The species is also regarded as probably extinct in Vietnam, and likely extinct as a breeding species in Thailand. It has undergone severe declines in China, Myanmar and Laos, and while it seems more secure in India, Nepal and Bangladesh, declines have been noted in those countries as well (Sykes 2010). In India, the species faces many threats, which include, in addition to those already listed, water extraction, disturbance and predation by cats, dogs and corvids attracted to human settlements, pollution from industry and agriculture, and mortality through fisheries bycatch (A. Rahmani in litt. 2010).

The widespread declines and ongoing threats raise the question of whether the currently inferred rate of global population decline is correct. If the available evidence were to suggest an overall decline of at least 30% over 27 years, the species could be eligible for uplisting under the A criterion. Up-to-date information is requested on the likely trends in this species’s population at national, regional and global scales. It has been suggested that its total population now numbers fewer than 10,000 mature individuals, which seems unlikely given the species’s range size; however, if evidence were to suggest this, the species could qualify for uplisting under the C criterion, thus current estimates for the species’s population size would also help in the assessment of its Red List status.

Goes, F., Claassen, A. and Nielsen, H. (2010) Obituary to the black-bellied tern. Cambodian Journal of Natural History 1: 5-6.

Sykes, B. (2010) River terns: is the Black-bellied Tern Sterna acuticauda heading to oblivion? BirdingASIA 13: 73.

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11 Responses to Archived 2011-2012 topics: Black-bellied Tern (Sterna acuticauda): request for information

  1. Samad Kottur says:

    I have been observing Black-bellied Tern in my place for more than 10 years. I have photographed these bird in Tungabhadra Dam during winter and early summer. I thing this species may be nesting in the back waters of T.B.Dam during late winter and early summer, as I have seen and photographed the bird in breeding plumage. But I have no photographic record of breeding of this bird in the back waters of T.B.Dam. But I have seen and photographed the breeding of Little Terns in this place. Here the population of Black-bellied Tern is pretty good along with River Tern, Little Tern, Whiskered Tern and Little Tern. A dedicated study is necessary to explore more about the Black-bellied Terns in our area. ie. Hospet , Bellary district, Karnataka. India.

  2. Jenny Daltry says:

    The correct citation for the Goes et al (2010) reference is:-

    Goes, F., Claassen, A. and Nielsen, H. (2010) Letter to the Editor – Obituary to the black-bellied tern. Cambodian Journal of Natural History, 2010 (1): 5-6.

    (If anyone wishes to see it, the 2010 volume (issues 1 and 2) can be downloaded from

  3. Paul Thompson says:

    To add to the information in Sykes 2010 for Bangladesh, there are some questions over identification of the few recent Bangladesh records. Compared with the 1990s other terns (River and Little) also seem scarcer on the Jamuna river. A more thorough survey would be needed to confirm this. The habitat is constantly changing, but in aggregate not reduced.

  4. I completely agree with Paul, we have never seen a Black-bellied Tern near the coast despite intensive visits. However, two were photographed in early Feb 2011 on the Jamuna river and one was seen in mid Feb 2011 at the same site.

  5. Carol Inskipp and Hem Sagar Baral says:

    In Nepal Black-bellied Tern is now a rare and very local visitor in the lowlands. It was assessed as Critically Endangered under the criteria A2a, C2a(i) and D1 in The State of Nepal’s Birds 2010 published by Bird Conservation Nepal and the Department of National Parks and Wildlife Conservation, Kathmandu. The species was very recently re-assessed under the same categories and using the same criteria for the Nepal Red Data Book which is currently being researched and written (to be published by the Zoological Society of London).The assessments were based on the decline in its population since at least the early 1990s and its very small population size. The distributional range of the species has also reduced since the early 1990s. In the 1970s it was considered fairly common on ponds and rivers of the terai, but now Black-bellied Tern is mainly only recorded from Koshi Barrage and Koshi Tappu Wildlife Reserve in the far east. The unusually high number of 60 was noted at Koshi Barrage in February 1984. The maximum annual number recorded at Koshi in 1994 was 14 in March 1994 and numbers gradually dwindled to five there by November 2011. Black-bellied Tern has also declined in Chitwan National Park. In the early 1980s it was considered a common resident and possible breeder in the park, but there are only a few recent records. The only other localities where the species has been seen since the early 1990s are Bardia National Park (2 records) and Sukla Phanta Wildlife Reserve (1 record).. Black-bellied Tern is severely threatened by food shortage and disturbance and destruction of its breeding habitats on rivers. A maximum current population of 20 has been estimated for the Nepal bird Red Data Book (in prep.).
    The above information is a summary of the species account written for the Nepal bird Red Data Book- a full account including references has been sent to Stuart Butchart and Mike Crosby at BirdLife.

  6. Joe Taylor says:

    The following comments were sent by Will Duckworth on 24 November 2011:

    Still perplexed that this species is listed only as NT given that things like Green Peafowl are EN! With the generally (and correct, in my view) somewhat precautionary stance of assignment of categories, surely the onus should be on credible comments from a significant pats of its range that it is not in steep decline. I don’t see this. Instead, look at the area of SE Asia and the rest of its range? SE Asia forms a high proportion. The species is effectively extinct there (enough info from Myanmar to say that it is not common on the Irrawaddy, at least, any more). Is the rationale that these declines happened too long ago to influence application of 3-gen based criteria? Since the species’s deline was not the result of targeted hunting for the E Asian medicine market or any other region-specific action, surely it is plausible (to the extent of being a default assumption pending evidence to the contrary) that the same process is occurring in S Asia? We already know from vultures in India that the declines in widespread aerial mobile birds can be of staggering magnitude before they are noticed by the general haphazard observation system.

  7. Simon Mahood says:

    Other than the birds on the Chambal river (how many are being seen there this year?) and Samad’s birds at Tungabhadra Dam (how many are there at that site?), is there anywhere else where more than a handful of BBT can be seen? You don’t mention the population in Pakistan on the Indus river, but I’m sure that threats there are the same as elsewhere on the Indian Subcontinent and the population equally tiny.

    You say above “It has been suggested that its total population now numbers fewer than 10,000 mature individuals, which seems unlikely given the species’s range size…” I would not be surprised if the population was already an order of magnitude less than 10,000, indeed it could be considerably less even than that.

  8. A few comments relating to Myanmar: During the last ten years I have participated in extensive boat-based surveys of wetlands in the Chindwin basin, especially along the Tenai and Chindwin Rivers. During these surveys (published as Tordoff et al in Nat. Hist. Bull. Siam Soc.) we did not record Black-bellied Tern. I have also done shorter boat based survey on the Irrawaddy River in its upper and middle reaches. Again we did not encounter this species. Along both rivers we encountered significant numbers of River Terns.

  9. Andy Symes says:

    Simon Mahood has added the following comment:

    I think there is a case for Black-bellied Tern being CR. It has gone from Vietnam, Laos and Cambodia (with certainty) and is almost gone completely/gone as a breeder from Myanmar and Bangladesh. There is no information for Pakistan but it is safe to assume that the situation there is the same as in India. Populations have declined rapidly and severely in Nepal and there are now no more than a handful of birds at any one site. In India there seems to only be one decent population at Chambal and a smattering of birds elsewhere which may occasionally breed. The situation is really dire. As for the size of the population at Chambal Colin Poole (WCS regional director and birder) was there last week and saw no more than a handful – Colin is sending me a comprehensive report soon with relevance to other river species and I will pass it on to you. I don’t know whether this massive range and population contraction fits the three generation time frame but this might not matter anyway since it would probably fit CR under Ca. As for reason for decline – massive human population increases throughout its range coupled with intense river use (development means sand and gravel extraction) and fishing – it just doesn’t seem to like disturbance. In the Indian Subcontinent House Crow has increased in number around human settlement, but since food supplies are often temporal big gangs of hungry crows roam the rivers searching for food – most bits of river are within crow flying distance of a human settlement. These guys eat anything – saw them trying to drown a Cotton Pygmy Goose and hassling Brown-headed Gulls every time they settled. I imagine they would make it impossible for a bird like Black-bellied Tern to breed successfully. Apparently some tern species, such as Little Tern, can withstand massive colony predation and still do ok, I get the feeling that BBT is not like this.

  10. Andy Symes says:

    Colin Poole has provided the following information from a visit to Chambal in January 2012:

    I saw 1 maybe 2 birds, and the guide I’d met who’d seen the 30 skimmers on another stretch had seen only 1. Everybody said they were much rarer than skimmers and always had been. Apparently they’re solitary nesters and sometimes nest on the same sand bank as the skimmers sometimes not. Come and go at similar times.

  11. Andy Symes says:

    Data on Black-bellied Tern from the Asian Waterbird Census is summarised below:

    Black-bellied Tern Sterna melanogaster NT
    1% = 250. The species is restricted to South and Southeast Asia. It was reported from 223 sites,
    mainly in South Asia, with three sites meeting the 1% criterion 1987-2007

    Country/Territory Region Site Name Peak Count Year
    India Gujarat Victor (-Bherai) Salt Pans & Coastal Area 305 2003
    India Orissa Chilika Lake Combined 282 1995
    Pakistan Sindh Rup (= Ghauspur, = Rap) Lake 300 2001

    Max Count 87-92: 168
    Max Count 93-97: 838
    Max Count 98-02: 461
    Max Count 03-07: 637

    The veracity of some of these large counts has to be called into question, however, due to the uncharacteristic habitat for Black-bellied Tern (coast and salt pans), and the strong possibility that some or all of these large counts relate to misidentified Whiskered Terns.

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