White-bellied Sea-eagle (Haliaeetus leucogaster): Revise global status?

BirdLife International factsheet for White-bellied Sea-eagle

White-bellied Sea-eagle is a Pacific raptor, with a range that stretches from western India through Indonesia to Australia (BirdLife International, 2020). The global population is estimated to be 1,000 – 10,000 individuals (Ferguson-Lees and Christie, 2001), which roughly equates to 670-6,700 mature individuals.

This species is threatened by human disturbance, including shooting and poisoning, and loss of breeding habitat (Ferguson-Lees and Christie, 2001). Previously, White-bellied Sea-eagle has been considered Least Concern, but a re-evaluation of its population size means this classification is no longer tenable and thus a complete reassessment of Red List category is required. We have therefore reassessed this species against all the criteria below.

Criterion A: The population trend for this species has not been calculated. We therefore cannot assess White-bellied Sea-eagle under Criterion A.

Criterion B: The Extent of Occurrence (EOO) for this species is >20,000 km². This species does therefore not qualify as threatened under this category, and so may be considered Least Concern under Criterion B1.

Criterion C: The global population size for White-bellied Sea-eagle is estimated to be 670-6700 mature individuals. This reaches the threatened threshold (<10,000 mature individuals), but in order to fully qualify for threatened status under criterion C, other sub-criteria must be met. White-bellied Sea-eagle is believed to be experiencing a continued decline from human disturbance and habitat loss, but it is not known to be undergoing any extreme fluctuations. While the mature individuals are not believed to exist solely in one subpopulation, the subpopulation structure remains unknown. If it transpires that <1,000 mature individuals are present in the largest subpopulation, then this species would qualify as threatened. At the moment, it does not fully qualify as Vulnerable under criterion C. We therefore seek any information about population structure: how many subpopulations are there, and how many individuals are in each one?

Criterion D: The global population size for White-bellied Sea-eagle is estimated to be 670-6700 mature individuals. Assuming the true population size is nearer the lower end of the estimate, this meets the threshold (<1000 mature individuals) for classification as threatened under this criterion. This species may therefore be considered Vulnerable under Criterion D1.

Criterion E: To the best of our knowledge, no quantitative analysis has been carried out on this species. We therefore cannot assess White-bellied Sea-eagle under criterion E.

We therefore suggest that White-bellied Sea-eagle (Heliaeetus leucogaster) be listed as Vulnerable under Criterion D1. We welcome any comments to the proposed listing.

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.

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.

References

BirdLife International (2020) Species factsheet: Haliaeetus leucogaster. Downloaded from http://www.birdlife.org on 18/05/2020.

Ferguson-Lees, J., and Christie, D.A., 2001. Raptors of the World. Christopher Helm, London.

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14 Responses to White-bellied Sea-eagle (Haliaeetus leucogaster): Revise global status?

  1. Yat-tung Yu says:

    White-bellied Sea Eagle is a resident species within the territory of Hong Kong. This species has been systematically surveyed (Tsim et al. 2003, So and Lee 2010) and the Hong Kong Bird Watching Society also collect observations and records of this species (and other wild birds in Hong Kong). After gathering all the sightings of this species in Hong Kong, there has a recent estimate of 15 breeding pairs found in different places scattered around Hong Kong. This breeding pair number in Hong Kong is likely increasing in the long term (Carey et al. 2001). The total land area of Hong Kong is 1,107 km square and this species is mainly found along the coasts and only found building nests on cliffs by the coast.

    Adults are apparently sedentary within the territory but no information about local movement of this species is available and hence dispersal of juvenile individuals is not known. We could not provide more clues about the size or range of the subpopulation in the neighboring area.

    Birdwatchers sometimes provide information and sightings of this species in neighboring areas, i.e. along the China coast. These anecdotal reports could not provide many comparable and systematic records for population estimate, but these still give hints that most of the White-bellied Sea Eagles were recorded closed to HK, indicating that the individuals might disperse away from Hong Kong. This species is generally quite rare along the South China coast.

    References
    Carey GJ, Chalmers ML, Diskin DA, Kennerley PR, Leader PJ, Leven MR, Lewthwaite RW, Melville DS, Turnbull M, and Young L. 2001. The Avifauna of Hong Kong. Hong Kong Bird Watching Society. Hong Kong.

    So IWY, Lee WH. 2010. Breeding Ecology of White-bellied Sea Eagle (Haliaeetus leucogaster) in Hong Kong –A Review and Update. Hong Kong Biodiversity. (18): 1-8.
    https://www.afcd.gov.hk/english/publications/publications_con/files/IssueNo18.pdf

    Tsim ST, Lee WH, Cheung CS, Chow GKL, Ma YN, Liu KY. 2003. The Population and Breeding Ecology of White-bellied Sea-eagles in Hong Kong. Hong Kong Biodiversity. (5): 1-7. https://www.afcd.gov.hk/english/publications/publications_con/files/hkbonewsletter5.pdf

  2. Simba Chan says:

    Yu Yat-tung has given a very good case study of its population and trend in Hong Kong, a territory that covers far less than 1% of the actual extend of occurence of this species. And by checking records on e-Bird this species has been commonly recorded from India to Australia. So I believe it is not appropriate to assume the true population is closer to the lower end of the rather outdated and probably underestimated information from Raptors of the World (Ferguson-Lees and Christie 2001). In the late 1990s when we compiled the BirdLife Red Data Book of Threatened Birds in Asia we held several workshops inviting ornithologists and conservationists from almost all Asian countries to discuss the list of threatened birds in Asia. That was probably the time when or after the drafts of the Raptors of the World was written. If the White-bellied Sea Eagle was a species of concern (i.e. less than 1,000 individuals) we should have included it in the RDB. But it seemed this species was still widespread and rather common then (we saw at least one at Kuala Selangor when we had one of the RDB workshops there in October 1995). I have not heard any suggestions that its situation is getting worse anywhere in the Asia-Pacific region.

  3. While no population trend data is available from Bangladesh, it is regularly seen in the Sundarbans (6,000km2) in the south-west and other coastal islands with mangroves. Out of my 33 visits to the Sundarbans since 2005, I have seen it on 26 occasions, although this only gives us presence and absence of the White-bellied Sea-eagle in the Sundarbans, which is believed to be the species’ stronghold in Bangladesh and possibly in South Asia. In addition, a nest was found in November 2019 on Hatia Island in the south-central coast of Bangladesh.

  4. Christoph Zockler says:

    From my work along the coast of Myanmar over the past 12 years I can also say that the species is still wide-spread on several coastal habitat types ranging from rocky coasts to mangroves. My rough estimate based on several surveys along the Rakhine coast, Mawdin coast (south of Rakhine), Ayeyarwady delta, GoM (scarce), Mon State and Tanintharyi (common) the species population is about 100-120 pairs in Myanmar. I have not observed any birds further inland and the species seems to remain restricted to coastal areas. There is also no specific threats noticed but breeding birds can be distubred by logging activities in mangroves in Taninthary, but no direct prosecution observed. I concur with Simba as not really threatened.

  5. Stephen Garnett says:

    If you visit the Bird Life Australia site https://birdata.birdlife.org.au/explore#from=2000-01-01&map=-27.6164756_136.9675549_4&species_id=226&to=2019-07-24 you will see that the species has a very wide distribution in Australia alone, with a population very likely to exceed 10,000, with a reporting rate that is completely flat. It is a common raptor regularly seen in most capital cities around the country including over the heart of Sydney

  6. Frederic GOES says:

    I agree with Simba Chan that classifying the species VU under criterion D1 would just be based on an unsupported and underestimated population assumption.

    I am pretty sure there must be some density estimates (number per km of coastlines) from several areas, and extrapolating those could give a more sensible population range limits. These sites could also form the basis for future trend assessment.

    Re criterion C, subpopulations need to be clarified: how to define them with such a species showing, although at variable density, near-continuous distribution along the coastal lines between India and Australia ?

  7. Robert Davis says:

    I agree with Stephen Garnett. The species is locally common in Australia including capital cities. Key offshore island groups including the Abrolhos Islands of Western Australia, support high numbers and breeding by this species. Based on the Australian population, VU would not seem warranted.

  8. Yong Ding Li says:

    Densely populated Singapore has at least 10-15 pairs, with nests in forest remnants. Langkawi (Malaysia), which is smaller, has likely more (and both are less than 1,000km2), as is Tioman (Malaysia, <400km2); even tiny Mantanani supports at least one pair. The species occurs in most coastlines in Southeast Asia, and there are no clear pattern of decline across its vast Indo-Malayan distribution (incl. the long Philippine coastline). And up-list does not seem strongly justified. The species however, may be trapped deliberately in parts of Indonesia (for the pet trade), but the volume is unclear.

  9. Praveen J says:

    “The population trend for this species has not been calculated. We therefore cannot assess White-bellied Sea-eagle under Criterion A.”

    While Criterion A cannot has not been evaluated globally, the trend in India was assessed in State of India’s Birds.

    https://www.stateofindiasbirds.in/species/wbseag1/

    It indicates a decline on -72.59% (CI 20.29%) in the long-term (Past 25y) and an annual decline of -5.89 (CI 10.98%) in the short term (last five years). The CI for short-term is too large to estimate current trends with confidence, however a long-term decline is suspected – specifically from pre-2000 to post-2000.

    As pre-2000 is an open ended period, it makes IUCN trend calculations difficult though it can be argued that the median is 25 years. As it creates an uncertainty in the declines that might need more justification, we decided to ignore this particular open-ended period. We created 10 decline intervals from the remaining time periods, and we used these decline intervals for red listing – with three generation for a species as the upper bound. If there is a decline in lesser number of years, then the decline would atleast be as much in the longer 3 generation interval (Except cases with extreme fluctuations). Using these intervals, we find –

    The optimistic estimate (upper bound of the 95% confidence interval) of the decline during 2007-2018 is -12.23% and the best estimate (mean) is -49.81%.

    Hence, there is evidence of some decline though the optimistic estimate 2007-2018 may not approach the thresholds of Vulnerable.

    However, it is to be noted that the 3-GEN period of White-bellied Sea-Eagle is much higher (1-GEN = 14.7y) and hence the declines would be higher if we consider a 3 -GEN period .
    http://datazone.birdlife.org/species/factsheet/white-bellied-sea-eagle-haliaeetus-leucogaster/details

    “We therefore seek any information about population structure: how many subpopulations are there, and how many individuals are in each one?”

    As seen from the map, there are atleast three sub-populations in India – (a) West Coast (b) East Coast & (c) Andamans. There are no population estimates available for these sub-populations.

    Suhel Quader, Praveen J and Ashwin Viswanathan

    For the SoIB partnership:
    Ashoka Trust for Research in Ecology and Environment
    Bombay Natural History Society
    Foundation for Ecological Security
    National Biodiversity Authority
    National Centre for Biological Sciences
    Nature Conservation Foundation
    Salim Ali Centre for Ornithology and Natural History
    Wetlands International South Asia
    Wildlife Institute of India
    Worldwide Fund for Nature—India

  10. 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

  11. Red List Team (BirdLife International) says:

    Following closure of the forums, we received a comment (via email) from a correspondent that further confirms a negative status of the species across some sites in India; however, we note that this may be unrepresentative of the overall population due to its widespread occurrence.

    • Red List Team (BirdLife International) says:

      The comment, submitted by S. Balachandran on 30th June is as follows:

      Southern India:
      In the 1980s in Southern India both at Point Calimere, and Gulf of Mannar (two islands Manali and Hare Islands, and Dhanuskodi in the Rameswaram Island ) four to seven nests around 10-15 individuals were frequently sighted. The frequency sighting both individuals and nests became scarce. But at Point Calimere last nest sighted was 2016 and that too not fledged successfully. Now at both the places occasionally seen either in single number or a Pair.

      Odisha Chililka Lake and adjoining area:
      Similar pattern has been observed at Odisha. In Nalabana Island every year one nest was observed on a small Ficus tree grown near the watch tower during 2001-2006. During that time nesting was regularly sighted till 2012 in three adjoining villages. Though two pairs are seen regularly on Nalabana Island till date no nesting happening. Even in the adjoining village some years one or two nests were sighted till 2018. It indicates some declining trend but not quantified. The frequency of sighting of this species was more on the Casuarina Plantation along the coastal road between Puri and Konark during 2002-2006. But during 2017 the frequency of sighting was relatively less. Lot of Casuarina plants along the coast were uprooted by cyclone Phailin in October 2013. But no quantitative estimates was done. As this species occurs in small numbers wherever it occurs except in Andamans, and the coast between Mumbai and Goa where I observed 10-15 nests during 2002. Their low recruitment rate and declining trend it may be included under Vulnerable category.

  12. Red List Team (BirdLife International) says:

    Preliminary proposal

    Based on available information, it is now considered that the population of the White-bellied Sea-eagle is not undergoing a significant decline as previously suspected. Whilst it is important to acknowledge higher decline rates occurring in India (as proposed by the State of India’s Birds [2020]), the species is known to be widespread across the general Indomalayan and Oceanian regions (eBird, 2020), of which across its Australian range, the population has recently seen a significant increase in population.

    Thus, our preliminary proposal for the 2020 Red List would be to keep the White-bellied Sea-eagle as Least Concern.

    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.

  13. Gopi Sundar says:

    Based on surveys (2017-2019) in the Gulf of Carpentaria region of Queensland, I would agree with Stephen Garnett that the species is very widely distributed.

    Along the Gulf, this species was commonly encountered scavenging on roadkill alongside several other raptors including kites and Wedgies.

    Proportion of young birds in the population varied between 10-44% annually suggesting some inter-annual variation in breeding, but our observations suggest that the species has a large and widespread breeding population in south-west Queensland.

    Swati Kittur, John Grant and Gopi Sundar.

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