African Fish-eagle (Haliaeetus vocifer): Request for information

BirdLife International factsheet for African Fish-eagle

The African Fish-eagle occurs across a large range in Africa. The range stretches from sub-saharan Senegal in the west, to Ethiopia in the east, and down to South Africa in the south (BirdLife International, 2020). It inhabits a range of aquatic habitats such as swamps, lakes, floodplains and estuaries (Ferguson-Lees and Christie, 2001). The population size is estimated to be >100,000 pairs (Ferguson-Lees & Christie, 2001).

The only known threat to this species is the potential egg-shell thinning resulting from the build up of organochlorine in their diet. While this was previously observed in South Africa (Ferguson-Lees and Christie, 2001) and Zimbabwe (del Hoyo et al., 1994), there was no evidence to suggest it was having a significant impact on the population. The population was therefore considered to be stable, and the species was subsequently listed as Least Concern.

However, new information suggests that in some areas of its range, the population of African Fish-eagles is declining, which may warrant a change in Red List status. Therefore, we have fully reviewed the species here against all criteria.

Criterion A – Declines have recently been reported for the African Fish-eagle. The rate of decline is measured over the longer of 10 years or three generation lengths of the species. The generation length for the African Fish-eagle has recently been recalculated to 12.3 years (Bird et al., 2020)*, meaning that trends should be assessed over 36.9 years (three generations) under this criterion.

A comparison of roadside counts that took place in 1969-1973 and in 2003-2004 across Mali, Burkina Faso and Niger detected a 100% reduction in the observation rate in unprotected areas (from 4.9 to 0 birds/100 km) and a 25% reduction in the observation rate in National Parks (from 2.8 to 2.1 birds/100 km; Thiollay 2006). Scaled across three generations (36.9 years), these rates of reduction equate to a 100% reduction in unprotected areas and a 28% reduction in National Parks.

A comparison of roadside counts that took place in 1973 and in 2004 in northern Cameroon detected a 98% reduction in the observation rate in unprotected areas (from 3.3 to 0.1 birds/100 km) and a 41% increase in the observation rate in protected areas (from 4.6 to 6.5 birds/100 km; Thiollay 2001, R Buij, unpublished data, in D. Ogada and P. Shaw in litt. 2020). Scaled across three generations (36.9 years), these rates of change equate to a 99% reduction in unprotected areas and a 51% increase in protected areas.

A comparison of roadside counts that took place in 1991-1995 and in 2015-2016 in northern Botswana detected a 52% reduction in the observation rate (from 0.25 to 0.12 birds/100 km) and reported a 63% decline, after controlling for variation in the lengths and distribution of survey transects (Garbett et al. 2018) Scaled across three generations (36.9 years), these rates of change equate to reductions of 71% and 81%, respectively.

In Kenya, during surveys in unprotected land between 1972 and 2012, too few birds were recorded to provide an estimate of change (Ogada et al., in prep. a).

However, new research into the rates of decline for this species is being conducted by Ogada et al., (in prep. b) who combined the changes in encounter rates described above, in protected and unprotected areas, weighted by the species’s range in each land use category, and within each country. This resulted in the following estimated reductions: 98% from 1969-1973 to 2003-2004 across Mali, Burkina Faso and Niger; 91% from 1973 to 2000 in northern Cameroon; and 63% from 1991-1995 to 2015-2016 in northern Botswana (Ogada et al. in prep. b). By weighting these reductions by the proportion of the species’s range within each survey areas, they estimated an overall rate of reduction of 9.5% per year. This would equate to a reduction of 97% over three generations (36.9 years). Data from a considerable part of the large range is lacking. While high decline rates have been reported from several countries, it is unclear whether the rates of reduction there are truly representative of the range-wide situation. Without more data from representative countries, it is difficult to gauge the full picture of the global decline rate. If sustained rates of decline are occurring across a wider area of its range, then the African Fish-eagle may warrant uplisting to a higher threat category. We therefore seek recent information on population trends for the African Fish-eagle throughout its range, particularly in countries such as South Africa, Zambia, Tanzania, Uganda, and Ethiopia. If this species is declining, we also seek information on the cause of declines. What are the threats, what are their trends, and how widespread are they?

Criterion B – The Extent of Occurrence (EOO) for this species is too large to trigger the threshold (EOO <20,000 km2) for threatened status under this criterion. African Fish-eagle may therefore be considered Least Concern under Criterion B1.

Criterion C – The population size estimate is too large to trigger the threshold for listing as threatened under this criterion (<10,000 mature individuals), and the African Fish-eagle is considered Least Concern under this criterion. The subpopulation structure for this species is  unknown, and a greater understanding of population size and sub-population structure would be beneficial. We therefore seek up-to-date information regarding population size and subpopulation structure.

Criterion D: The global population size estimate is far too large to reach the threshold (<1,000 mature individuals) for classification as threatened, and so this species is considered Least Concern under this criterion. However, we seek up-to-date information on population size for African Fish-eagle.

Criterion E – To the best of our knowledge, no quantitative analysis of the probability of extinction has been done for this species. We therefore cannot assess the African Fish-eagle against this criterion.

To carry out a comprehensive reassessment of the Red List status of African Fish-eagle, we therefore ask for recent information on the population size and trend from as many African countries as possible, as well as on the subpopulation structure.

* 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).

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

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

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

del Hoyo, J.; Elliott, A.; Sargatal, J. 1994. Handbook of the Birds of the World, vol. 2: New World Vultures to Guineafowl. Lynx Edicions, Barcelona, Spain.

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

Garbett R; Herremans M; Maude G; Reading RP; Amar A. 2018. Raptor population trends in northern Botswana: a re-survey of road transects after 20 years. Biological Conservation 224: 87–99.

IUCN Standards and Petitions Committee, 2019. Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Committee. Downloadable from http://www.iucnredlist.org/documents/RedListGuidelines.pdf.

Ogada, D., Shaw, P., Virani, M.Z., Thiollay, J.M., Kendall, C.J., Odino, M., Patel, T., Wairasho, P., Dunn, L., Thomsett, S., in prep. a. Raptor declines in Kenya over the past 45 years.

Ogada, D., Shaw, P., Buij, R., Thiollay, J.M., Garbett, R., Herremans, M., Virani, M.Z., Amar, A., Maude, G., Dunn, A., and Thomsett, S., in prep. b. Continental declines of Africa’s raptors.

The Cornell Lab for Ornithology, 2020, Range Map for African Fish-eagle Haliaeetus vocifer, available at https://ebird.org/species/affeag1 accessed 05/05/20

Thiollay, J.M. (2001). Long-term changes of raptor populations in northern Cameroon.  J. Raptor Res. 35: 173-186

Thiollay, J.M., 2006, The decline of raptors in West Africa: long-term assessment and the role of protected areas, Ibis, 148, pp. 240-254

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10 Responses to African Fish-eagle (Haliaeetus vocifer): Request for information

  1. Chris Brewster says:

    In south-east Botswana African Fish Eagle is one of the very few raptors that is doing well (The only other raptor clearly doing well is Lanner Falcon). It is present at all waters where its prey, fish, is present – in SE Botswana, these waters are generally dams as there are no natural wetlands. The species would not be missed on roadside counts – to record the species visits must be made to dams. There is no evidence of decline, unlike nearly all large raptors which have declined greatly in SE Botswana

  2. James Westrip says:

    To really assess the trend of this species data is really required from wetland areas, rather than just basing things on roadside counts. In South Africa it is common, and as mentioned in a previous comment, this species responds well to the creation of artificial water sites – this is also a reason it was not included in Taylor et al. (2015); in effect making it LC in this region.

    In South Africa it can also be seen even in urban areas (e.g. on the Orange River in Upington); so I would be very surprised if the rates of decline as outlined in this post are actually occurring in this part of its range.

    In Namibia it is listed as Vulnerable, but not based on rates of decline, instead under criterion D – this can be found through http://www.the-eis.com

    Reference
    Taylor et al. (2015) The 2015 Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland.

  3. Shiv Kapila says:

    African Fish Eagles are doing very well, locally, in Kenya. Surveys of Kenyan Rift Valley lakes over the past 50-60 years have of course recorded fluctuations, but numbers are at an all time high at Lake Naivasha, one of this species’ Kenyan strongholds – the last dedicated count here recorded 245 adult birds (2017) over 68 kilometres of lakeshore, and recent waterbird surveys have recorded 300+ mature birds, more than was ever recorded in the 50s and 60s, before any habitat loss, and human disturbance.

    As this species can be thought of as a definite waterbird, road counts will greatly underestimate numbers, and fluctuations/decreases on such surveys are all down to luck (some birds will be seen in poor habitat, dry habitat etc., but these are all likely to be vagrants, or juveniles and subadults moving between permanent water). Ideally, a good handle on numbers can only be ascertained by boat surveys, on large, permanent waterbodies – rivers, lakes, dams, coastlines, and not by road.

  4. Paul Gacheru says:

    In Kenya, annual waterbird counts have been carried out since 1993. In this organized systematic surveys have recorded all water birds including raptors. We summarised data of African Fish eagle of between 2010 to 2018 and there is a clear indication that the population within the RiftValley Lakes in Kenya, is on the increase. This is captured in the 2018 Kenya KBAs Status and Trends Report.

  5. Our research team conducted >10,800km of raptor roadcounts throughout the extent of Ethiopia from 2010 – 2017 and, of 22,909 individual raptors recorded, we recorded only 35 African Fish-eagles (0.15% of raptors observed; 0.003 individuals/km). However, these surveys were not specifically designed to sample African Fish-eagle, as the species is highly associated with water bodies. In a single boat survey of Lake Hawassa on November 6, 2018 we covered approximately 16km of shoreline over 36 minutes and counted 47 individual African Fish Eagles, most of which were breeding pairs near visible and apparently active nests. This indicates that the rift valley lakes of Ethiopia could harbor many hundreds if not thousands of breeding fish eagles, and warrants further study. However, the African Fish Eagle faces increasing pressure from the large and growing human population size in the country, serious degradation of water quality and development of shoreline habitat, and limited protection even within flagship national parks in the country.

    Evan R. Buechley, PhD
    International Program Director
    HawkWatch International

  6. 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

  7. Red List Team (BirdLife International) says:

    Preliminary proposal

    Due to the ecology of this species, road count surveys are not a suitable way to assess population trends, and as such we cannot base a Red List assessment for this species on road survey data. The evidence provided from wetland areas suggests that the African Fish-eagle is stable to increasing.

    Our preliminary proposal for the 2020 Red List would therefore be to retain African Fish-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, following further checking of information relevant to the assessments by both BirdLife and IUCN. The final publication date will be publicised by IUCN here: https://www.iucnredlist.org/assessment/updates

  8. Neil Deacon says:

    Within Zimbabwe, African Fish-eagles seem to be doing very well and have benefited from a proliferation of farm dams and larger impoundments, despite early concerns over the effects of D.D.T. Their numbers appear to be increasing and now even occur and nest within urban areas, where ever there are permanent water bodies. Data in support of these observations could be extracted from biannual waterfowl counts if necessary. They have adapted to preying on Nile Tilapia (Oreochromis niloticus) and Largemouth Bass (Micropterus spp.), both alien species which have invaded and replaced a suite of indigenous cichlids (‘Tilapias’) from most of our river catchments, particularly in any dams or impoundments. The only apparent threat that might impact Fish-eagles into the future is the effect of a massive increase in the artisanal gill-net fishery based predominantly on cheap, non-biodegradable nylon mono-filament gill-nets. There is increased incidence of entanglement and individuals with gill-net fragments wrapped around their feet and legs are often seen. We have not attempted to quantify this threat yet, but there is an increase in unregulated artisanal gill-netting fishing on inland waters in most southern African countries.

  9. Red List Team (BirdLife International) says:

    The following comment was received by email from Darcy Ogada and Phil Shaw:

    Reporting rates for African Fish Eagle in South Africa increased by 43% between SABAP1 (1987–1992) and SABAP2 (2007–2020). This is equivalent to an annual increase of 1.5% (over c. 24 years), or +72% when projected over three generation lengths (36.9 years).

  10. Tanzania is a WET country and while Fish Eagle densities are low along some stretches of coastline and on rivers such as the Ruvuma and lakes such as Tanganyika and Nyasa this bird is just about everywhere one would expect it. In Tanzania, roadside counts would be of little value for this species. 4,208 records on our database. Maps available on request. Our 1995 waterbird count suggested a density in excess of 4 birds per km of shoreline in the SW corner of Lake Victoria with 621 birds on Rubondo Island. My population guesstimate for the country was 15-20,000 birds, perhaps towards the lower end.

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