Damara Tern
Sternula balaenarum
Number Of Mature
Individuals (Regional)
104
Regional
Population Trend
Decreasing
2025
Regional Category
Endangered
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CONTENTSOverview
Names
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IOC English Name: |
Damara Tern |
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SA & IOC Scientific Name: |
Sternula balaenarum |
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BirdLife International Taxonomy (scientific name): |
Sternula balaenarum |
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Order: |
CHARADRIIFORMES |
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Family: |
Laridae |
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Species name author: |
Strickland 1853 |
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Afrikaans: |
Damarasterretjie |
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Sesotho (South Africa): |
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Sesotho (Lesotho): |
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Siswati: |
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Zulu: |
unonklilwane wakwelaBathwa |
Current Assessment Status
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2025 Regional Category [Criteria] |
EN [A2abc; C1+2a(i); D] |
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2024 Global Category [Criteria] |
LC |
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Population size (Regional) |
52 pairs (Martin et al. 2024) |
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Population size (Global) |
2200 – 5700 mature individuals (BirdLife International 2024) |
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Distribution size (EOO) (Regional) km2 |
c. 190 000 |
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Distribution size (EOO) (Global) km2 |
1 350 000 (breeding/resident) |
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Distribution size (AOO) (Regional) km2 |
c. 3312 |
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Generation time |
12.33 years (Braby et al. 2024a) |
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Status change reason |
Improved Information |
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Migrant (in the region) |
Resident and breeding visitor |
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Regional endemic |
No |
Historic Listing Information
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2000 Regional Status |
EN [A2c; C2a; D1] |
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2015 Regional Status |
CR [C1] |
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Status change reason (if applicable) |
Genuine (recent) |
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2015 Global Status |
NT [C2a(i)] |
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2015 Population size |
70 – 100 mature individuals |
Reason for Inclusion
Reason for Inclusion in the Assessment
>5% of the global range of this species lies within the region. The species has been globally Near Threatened, then Vulnerable from 2016 to 2021, and is currently Least Concern. It was assessed as regionally Endangered in 2000, and regionally Critically Endangered in 2015.
Category Justification
Category Justification
The regional population of Damara Tern Sternula balaenarum nearly satisfies requirements for Critically Endangered under the small population size criterion C1 – with a population size estimated to number <250 mature individuals and an estimated continuing decline of 24.7% over 1G – from 65 pairs in 2010 to 52 pairs in 2021. As outlined in Martin et al. (2024), the Damara Tern population in South Africa also satisfies several further Endangered criteria, namely A2abc, C1, C2a(i), and D.
Population Justification
The most recent estimate of the global population was 773 pairs in 2021/22: consisting of 6 pairs in Angola, 715 in Namibia and a regional population of 52 (Braby et al. 2024a). Martin et al. (2024) estimated there to be 52 pairs in South Africa between 2018 and 2021. Confidence in the regional population estimate is high.
Trend Justification
The global population is considered to be decreasing (BirdLife International 2024). Minimum estimates of the global population fell from 1001 pairs in 2010 (Braby 2011) to 773 pairs in about 2021 (Braby et al. 2024a, Martin et al. 2024), i.e. by c. 23% in 11 years or 25.5% in 1G.
The declining trend is reflected in South Africa. In the late 1970s c. 150 pairs of Damara Terns bred in South Africa (Cooper et al. 1984). Underhill (2000) then estimated c. 100 pairs, which was potentially optimistic (Crawford et al. 2012), and Braby (2011) estimated 65 – 148 pairs, of which the majority (44 – 115 pairs) were in the Northern and Western Cape. Crawford et al. (2012) estimated just 36 pairs based upon 4 – 11 pairs at De Mond Nature Reserve in Western Cape, and 25 pairs in Eastern Cape. A once thriving colony at Struisbaai (11 – 13 pairs in the early 2000s) declined to four pairs by 2018 (Williams et al. 2004, Martin et al. 2024). In 2018-2021 there were an estimated 52 pairs breeding in South Africa with all but nine pairs from the Eastern Cape. The observed decrease of 65% in breeding pairs from c. 150 to c. 52 over the 40 years 1980-2020 equated to a decrease of c. 60% in 3G. The 20% decrease from c. 65 pairs in 2010 to c. 52 pairs in 2018-2021 equated to a decrease of 24.7% in 1G (Martin et al. 2024). Confidence in the trend estimate is high.
Biology & Ecology
Taxonomy
This species was previously in the genus Sterna and was reclassified along with several similarly small terns as Sternula.
Identification
A small tern, measuring 22–23 cm and weighing 52 g. Adults have a distinctive dark brown cap appearing black in the field. The cap extends below the blackish-brown eye, starting from the base of the lower mandible. The upper body is uniform grey, while the tail, underwing, and belly are white. Outer primaries are darker grey than the inner ones. It has a sharp black bill with a yellow base, and dull yellow legs, though often inaccurately shown as black in field guides (Simmons 2005).
Distribution
The species breeds in Angola, Namibia and South Africa (Crawford and Simmons 1997, Simmons 2005) with maximum densities occurring in the Walvis Bay region, Namibia, and decreasing to the north and south of this coastal town (Simmons et al. 1998). Distribution extends c. 150 km north into Angola, although only one breeding colony has been located in that country, 30 km north of the Cunene River (Simmons et al. 2010). Outside of the breeding season, the majority of the population is distributed in West Africa, including Benin and Ghana, with Namibian ringed birds being recovered in Nigeria. Since 2018, birds from the Eastern Cape of South Africa have been found wintering on the San Sebastian Peninsula, Mozambique (Allport et al. 2022, Martin et al. 2024). Within the region, the species is confined to just 14 breeding localities from Alexander Bay, Northern Cape, to the Alexandria Dune Fields in Eastern Cape, but six are no longer used (Martin et al. 2024). The species is uncommon in South Africa, with the largest concentration occurring in the Alexandria Dune Fields, east of Port Elizabeth (Braby et al. 2011, Crawford et al. 2012, Martin et al. 2024). Coastal distribution is probably related to small-fish availability as much as it is to breeding habitat, because higher densities of breeding terns occur where the greatest offshore productivity occurs (Simmons and Cordes 2000). The Damara Tern is found at four IBAs, namely Orange River Mouth Wetlands (SA030), Woody Cape Section: Addo Elephant National Park (SA094), De Hoop Nature Reserve (SA119) (although no longer breeds there (see Martin et al. 2024 for source) and was last recorded there in 2008 on the second Southern African Bird Atlas Project (SABAP2)) and Heuningnes River Estuary System (SA121).
Ecology
Damara Terns occur along high-energy desert coasts during the non-breeding season and in sheltered bays and shallow reefs during the breeding season (Braby et al. 1992). Salt pans, gravel plains and gravel slacks close to the ocean are favoured nesting areas in South Africa (Watson and Kerley 1995, Underhill 2000), while salt pans (southern Namibia) and large gravel plains (northern Namibia) are favoured elsewhere (Simmons et al. 1998). Damara Terns breed mainly from November to March, with variation according to location. The clutch size is typically a single egg (Braby 2011); this is unusual for small terns that more often lay two eggs. Nest location in Namibia is influenced by jackal activity: nests are located farther inland where density of jackal tracks at the coast is high (RE Simmons, R Heber-Percy and J Braby unpubl data). In South Africa, jackals are less problematic and colonies tend to be closer to the ocean (J Cooper pers comm). Presence of jackals and humans influences success of nests; reducing disturbance can double the production of chicks in protected colonies (Williams et al. 2004, Braby et al. 2009). The species rarely roosts with other terns on the coast (Simmons et al. 2010). Long-term studies indicate that immature survival from fledging to adulthood is high at 0.59 and individuals start to breed at 3–4 years of age (Braby et al. 2011). Annual adult survival is high at 0.88 and the probability of a breeding bird moving to another colony is low at 0.06 (Braby et al. 2011). These statistics indicate that adult birds are long lived and are faithful to their breeding colonies. The generation length of 12.33 years was calculated from published estimates of mean age at first breeding and mean annual adult survival (Braby et al. 2024a). Birds forage mainly over shallow water, often in bays, over reefs, or in salt works, probably because surf-zone fish are concentrated there and less often in open water (B Clark pers comm). Terns also plunge dive for fish behind breakers in the open ocean and may do so at night (Braby et al. 1992). Foraging birds tend to avoid murky, sediment-filled water in preference for clear water (Simmons and Braine 1994, Braby 2011). Damara Terns feed on small fish that are rarely longer than a bill length (3 cm), including needle fish (Tylosaurus species), larval blennies (Blennidae), Cape Silverside Atherina breviceps, and Cape Anchovy Engraulis encrasicolus (Clinning 1978, Simmons and Braine 1994, Braby 2011).
Threats & Conservation
Threats
Off-road vehicle disturbance which leads to nest desertion and direct fatalities due to crushed eggs and chicks, is a large threat to Damara Tern colonies (Braby et al. 2009, Braby 2011). Habitat destruction has also led to the loss of colonies (Braby et al. 2024b). In Namibia, diamond mining is a known threat leading to habitat loss (Simmons 2005). A colony near Walvis Bay recently went extinct due to residential development where the birds were nesting (Braby 2011). Tidal flooding of low-lying colonies and attraction of predators (such as seals) to colonies, e.g. through discarding fish offal nearby (Braby 2011, Simmons et al. 2015) have also contributed to the population decline.
In South Africa, banning of off-road vehicles on beaches reduced disturbance and increased breeding success (Williams et al. 2004) but the threat remains at colonies in the Northern, Southern and Eastern Cape. For instance, off-road driving and municipal dumping wiped out the important colony at Port Nolloth Pan in the Northern Cape province (Crawford et al. 2018). Several colonies, such as Port Nolloth and Karas Pans, have been lost due to habitat destruction (Crawford et al. 2018). Diamond mining is a threat in the Northern Cape, whether legal or illegal (illegal diamond mining is suspected at Kleinzee). Sand mining threatens one of the colonies near Coega (Martin et al. 2024). Increasing the likelihood of predation is another important anthropogenic threat (Braby 2011). Human presence has caused a rise in jackal, gull, and seal densities.
Climate-related threats to the terns, and other fish-eating species, come from possible consequences of wind reduction driving the Benguela upwelling in turn affecting primary productivity and fish populations available to all marine species. The level of this threat is, however, hard to gauge. Altered climate may also increase flooding of coastal nesting sites (Braby et al. 2024a). Swamping of eggs by wind-blown sand is the major cause of mortality in the Struisbaai colony (AJ Williams unpubl data). The spread of non-indigenous, invasive vegetation on dunes may have affected some breeding sites in the Western Cape (J Cooper pers comm).
When species are under pressure from threats to their survival, their reproductive success is affected. Species at low population sizes have reduced fitness, further compounding the work needed for the population to recover. The low population size is a threat itself (Frankham 2005).
Conservation Measures Underway
In South Africa, the Department of Environmental Affairs banned off-road vehicles from all beaches in 2001, which had an immediate positive effect on shorebirds in South Africa (Williams et al. 2004). Protection from vehicles had a similar effect on productivity in Namibia (Braby et al. 2009). If the Damara Tern is classified as globally Endangered, as recommended (Braby et al. 2024b), breeding sites with at least 15 individuals or five breeding pairs will qualify as Important Bird Areas (BirdLife International 2020).
Conservation Measures Proposed
Given that disturbance and mining are probably the biggest source of mortality and colony abandonment, vigilance in keeping all colonies undisturbed, and protecting them formally (Martin et al. 2024), are priorities for the few colonies remaining in South Africa. Additionally, there needs to be some liaison with states to which birds migrate in the non-breeding season to ensure their protection in these non-breeding range states. Monitoring of populations needs to be undertaken and published. Organic waste control to reduce scavengers and predators (Simmons et al. 2015) is needed (Simmons et al. 2015). A Population and Habitat Viability Assessment (PHVA) and Biodiversity Management Plan, culminating in a National Species Recovery Plan are also recommended.
Research Priorities and Questions
- Reasons for abandonment of breeding sites (such as the colony at Dreyer’s Pan near Kleinzee) and breeding range shifts should be investigated. Regarding shifts, it would be useful to know:
- Reasons for the shift in the Struisbaai breeding site from near Heuningnes Estuary to near Struisbaai car park, and
- Reasons for the shift or extension to their breeding range in the Alexandria dunefields, as summarised in Martin et al. (2024).
- Studies on diet composition and linkages with relevant fish populations need to be undertaken.
- To improve demographic information available for South African colonies, i.e. estimates of breeding success (chicks fledged per pair), age at first breeding, breeding frequency (do adults skip breeding in some seasons), juvenile and adult mortality/survival and interchange between colonies (including Namibian) – and how site fidelity may be affected by disturbance.
- To investigate factors that may be driving changes in demographic parameters and shifts in the breeding and over-wintering distributions of Damara Terns (one shouldn’t presuppose El Nino Southern Oscillation is the driver; it could be long-term change in winds, currents, temperatures etc., or anthropogenic activities such as sand mining and human access to localities).
Contributors & References
Assessor/s
Philip A Whittington
Reviewer/s
Robert JM Crawford, A. Paul Martin
References
Allport GA, Gilroy D, Reed C. 2022. The status and distribution of three species of Sternula terns on the eastern coast of Africa and in the western Indian Ocean, with two species new for Mozambique. Bulletin of the British Ornithologists’ Club 142: 190–208.
BirdLife International. 2020. Guidelines for the application of the IBA criteria. Final version, July 2020. 18 pp. Available at: http://datazone.birdlife.org/. [Accessed on 20 May 2022].
BirdLife International. 2024. Species factsheet: Damara Tern Sternula balaenarum. Available at: https://datazone.birdlife.org/species/factsheet/damara-tern-sternula-balaenarum/details. [Accessed on 25 October 2024].
Braby R, Braby S, Simmons R. 1992. 5000 Damara Terns in the Northern Namib Desert – a reassessment of world population numbers. Ostrich 63: 133-135.
Braby J, Braby RJ, Braby N, Simmons RE. 2009. Protecting Damara Terns Sterna balaenarum from recreational disturbance in the Namib Desert increases breeding density and overall success. Ostrich 80: 71–75.
Braby J. 2011. The biology and conservation of the Damara Tern in Namibia. PhD thesis, University of Cape Town, South Africa. p 233.
Braby J, Braby SJ, Braby RJ, Altwegg R. 2011. Immature survival and age at first breeding of Damara Terns: conservation from a non-breeding perspective. Ardea 99: 185–190.
Braby RJ, Braby J, Braby S, Simmons RE, Crawford RJM. 2024a. Numbers, trends, and conservation of Damara Terns (Sternula balaenarum) in Namibia and Angola: a re-assessment of their IUCN conservation status. In: Makhado AB, Amaro A, Crawford RJM, Gottlieb TR, Morais M, Mwaala DN, Nghimwatya L, Seakamela M, Tom DB, Whittington PA, Witteveen M (eds). Atlas of marine turtles, seabirds, and seals in the Benguela Current and adjacent regions. Population sizes and trends, conservation status, and Important Bird and Biodiversity Areas for breeding. Cape Town, South Africa: Benguela Current Convention, Swakopmund, Namibia and Department of Forestry, Fisheries and the Environment.
Braby RJ, Martin AP, Whittington PA, Crawford RJM. 2024b. The overall status of Damara Terns (Sternula balaenarum). In: Makhado AB, Amaro A, Crawford RJM, Gottlieb TR, Morais M, Mwaala DN, Nghimwatya L, Seakamela M, Tom DB, Whittington PA, Witteveen M (eds). Atlas of marine turtles, seabirds, and seals in the Benguela Current and adjacent regions. Population sizes and trends, conservation status, and Important Bird and Biodiversity Areas for breeding. Cape Town, South Africa: Benguela Current Convention, Swakopmund, Namibia and Department of Forestry, Fisheries and the Environment.
Clinning CF. 1978. The biology and conservation of the Damara tern in South West Africa. Madoqua 11: 31-39.
Cooper J, Williams AJ, Britton PL. 1984. Distribution, population sizes and conservation of breeding seabirds in the Afrotropical region. In: Croxall JP, Evans PGH, Schreiber RW (eds), Status and Conservation of the World’s Seabirds: ICBP Technical Publication. Cambridge: International Council for Bird Preservation. 2: 403–419.
Crawford RJM, Simmons RE. 1997. Damara Tern Sterna balaenarum. In: Harrison JA, Allan DG, Underhill LG, Herremans M, Tree AJ, Parker V, Brown CJ (eds). The atlas of southern African birds Vol I: Non-passerines. Johannesburg, South Africa: BirdLife South Africa. pp 480-481.
Crawford RJM, Dyer BM, Kotze PGH, McCue S, Meÿer MA, Upfold L, Makhado AB (eds). 2012. Status of seabirds breeding in South Africa in 2011. Cape Town, South Africa: Oceans and Coasts, Department of Environmental Affairs.
Crawford RJM, Dyer BM, Geldenhuys L, Oosthuizen WH, Makhado AB. 2018. Seabird breeding populations decrease along the arid coastline of South Africa’s Northern Cape province. Ostrich 89: 299-305.
Frankham R. 2005. Genetics and extinction. Biological Conservation 126(2): 131-140.
Martin AP, Whittington PA, Dyer BM, Crawford RJM, Makhado AB. 2024. Numbers, trends, status and conservation of Damara Terns (Sternula balaenarum) in South Africa. In: Makhado AB, Amaro A, Crawford RJM, Gottlieb TR, Morais M, Mwaala DN, Nghimwatya L, Seakamela M, Tom DB, Whittington PA, Witteveen M. (eds). Atlas of marine turtles, seabirds, and seals in the Benguela Current and adjacent regions. Population sizes and trends, conservation status, and Important Bird and Biodiversity Areas for breeding. Cape Town, South Africa: Benguela Current Convention, Swakopmund, Namibia and Department of Forestry, Fisheries and the Environment.
Simmons RE, Braine S. 1994. Breeding, foraging, trapping and sexing of Damara Terns in the Skeleton Coast Park, Namibia. Ostrich 65: 264–273.
Simmons RE, Cordes I, Braby R. 1998. Latitudinal trends, population size and habitat preferences of the Damara Tern Sterna balaenarum on Namibia’s desert coast. Ibis 140: 439–445.
Simmons RE, Cordes I. 2000. Why is shorebird density so high in Walvis Bay? Delayed blooming and Benguela upwellings. African Journal of Aquatic Science 25: 229.
Simmons RE. 2005. Damara Tern Sterna balaenarum. In: Hockey PAR, Dean WRJ, Ryan PG (eds). Roberts – Birds of Southern Africa (7th Edn). Cape Town, South Africa: The Trustees of the John Voelcker Bird Book Fund. pp 464– 465.
Simmons RE, Kemper J, Braby J. 2010. Elizabeth Bay Optimisation Study. Unpublished report. Windhoek, Namibia.
Simmons RE, Braby RJ, Braby SJ. 2015. Damara Tern Sternula balaenarum (Sterna balaenarum). In: Simmons RE, Brown CJ, Kemper J (eds). Birds to watch in Namibia: red, rare and endemic species. Windhoek: Ministry of Environment and Tourism and Namibia Nature Foundation. pp 91–95.
Underhill LG. 2000. Damara Tern Sterna balaenarum. In: Barnes KN (ed). The Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland. Johannesburg, South Africa: BirdLife South Africa. pp 45–47.
Watson JJ, Kerley GIH. 1995. A survey of the dune-breeding birds in the Eastern Cape, South Africa. Ostrich 66: 15–20.
Williams AJ, Ward VL, Underhill LG. 2004. Waders respond quickly and positively to the banning of off-road vehicles from beaches in South Africa. Wader Study Group Bulletin 104: 79–81.
Citation
Whittington PA 2025. Damara Tern. In: Lee ATK, Rose S, Banda S, Bezeng SB, Maphalala MI, Maphisa DH, Smit-Robinson H (eds), The 2025 Red Data Book of Birds of South Africa, Lesotho and Eswatini. Johannesburg, South Africa: BirdLife South Africa. Available at: https://www.birdlife.org.za/red-list/damara-tern/
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