Page 536 - Atlas Sea Birds Ver1

3.14 Numbers, trends, status, and conservation of Caspian
Tern (Hydroprogne caspia) breeding coastally in southern
Africa

Authors: RJM Crawford, BM Dyer, C Fox, AP Martin, M Morais, DB Tom, L Upfold, PA Whittington, and AB Makhado

Abstract:
Caspian Terns (Hydroprogne caspia) have a widespread global distribution. However, those in southern Africa (including Angola) are
isolated from birds farther north and are regarded as a discrete population. They are known to have bred at 43 sites in the region, of which
38 are coastal and five are inland sites. From 1980–1991, the entire southern African population was estimated to number 501 pairs, of
which about 90% bred coastally. The recent coastal population was c. 318–396 pairs. If the overall population is < 1,000 mature individuals,
it should be classified as regionally Vulnerable in terms of criteria of the International Union for Conservation of Nature, although the global
population is of Least Concern. Lake St Lucia, in northeast South Africa, held c. 40% of the recent coastal population and was the only
site where > 100 pairs nested. Seven other coastal sites (one in Angola, two in Namibia, and four in South Africa) also recently held ≥ 10
pairs, so that eight sites were identified as potential Important Bird and Biodiversity Areas in terms of guidelines recommended by BirdLife
International. Major threats to the region’s Caspian Terns include predation by carnivores and disturbance by humans at mainland sites,
and loss of breeding habitat caused by altered management practices, urban development, or natural events at coastal sites.
Introduction:
The Caspian Tern (Hydroprogne caspia) occurs in North America, Baltic Europe, central and south Asia, Australia, New Zealand,
Madagascar, and Africa. North American and European birds migrate south after breeding, the latter travelling to west and central Africa,
approximately to the equator, and the Middle East (del Hoyo et al. 1996). The species is also a breeding resident in west and southern
Africa, where it disperses over short distances (Simmons 2015). Young Caspian Terns from Algoa Bay on South Africa’s south coast
moved to southern Mozambique, where no breeding is known to occur, and later returned to Algoa Bay (Underhill et al. 1999). The world
population of Caspian Terns was estimated as 50,000 pairs in 1996 (del Hoyo et al. 1996) but between 240,000–420,000 mature individuals
in 2006 (Dodman and Diagana 2006 in Ortmann et al. 2015). In 2022, the species’ global population was thought to be increasing and it
was classified by the International Union for Conservation of Nature (IUCN) as Least Concern (Birdlife International 2022).
Southern African Caspian Terns, including those in Angola, are isolated from birds farther north (Cooper et al. 1992) and are considered
a discrete population (AEWA 2015, Simmons 2015). By 1992, Caspian Terns had been recorded breeding at 28 sites in southern Africa
but had ceased to do so at the Zambezi estuary in southern Mozambique. The other 27 sites comprised 23 coastal sites, four in Namibia
and 19 in South Africa, and four inland waterbodies, three (Barberspan 26.55° S, 25.60° E; Vaal Dam 26.88° S, 28.12° E; Kalkfontein Dam
29.50° S, 15.25° E) in central-north South Africa and one (Sua Pan at Nata Delta, 20.50° S, 26.00° E) in Botswana (Cooper et al. 1992).
By 2022 breeding had been recorded at 14 more coastal sites, one in Angola, four in Namibia and nine in South Africa, and at Gariep Dam
(30.64° S, 25.68° E) in central South Africa (Marnewick et al. 2015), bringing the known number of breeding sites in southern Africa to
43, of which 38 were coastal. These numbers consider Berg River Estuary, Swartkops River Estuary and Lake St Lucia each to be single
sites. Caspian Terns have bred at three sub-sites in the Berg River Estuary (Upfold et al. 2024), three in the Swartkops River Estuary
(Martin and Whittington 2024), and six at Lake St Lucia (Fox et al. 2024). The locations of the sites at which Caspian Terns are known to
have bred in southern Africa are shown in Figure 1. They include islands along the coast, salt pans and small islands or beaches in pans,
dams, estuaries, and lakes (Tree 2005, Dyer 2007, Bowker and Downs 2012, Simmons 2015). Caspian Terns feed almost entirely on
fish that are caught in clear, shallow water at inland or marine environments, in the latter instance within 100 m of the coast (Tree 2005).
This chapter updates estimates of numbers of Caspian Terns breeding in southern Africa. It makes a preliminary assessment of the
Red List status of, identifies Important Bird and Biodiversity Areas (IBAs) for, and summarises threats to the southern African coastal
population.

Numbers and distribution

In 1972, it was thought that 500–1,000 pairs of Caspian
Tern bred at Lake St Lucia on KwaZulu-Natal’s north coast
(Berruti 1980). From 1980–1991, the entire southern African
population was estimated to number 501 pairs, of which
45 pairs (9%) bred at two inland sites and 456 pairs (91%) at
15 coastal sites. At that time, about 290 pairs bred at Lake
St Lucia (Cooper et al. 1992). In 2006, c. 425 pairs bred
coastally in Angola, Namibia, and South Africa (Kemper
et al. 2007). In 2015, the Namibian population averaged
about 160 birds, the South African coastal population
300–316 pairs, and the Caspian Tern was adjudged to be
Vulnerable (VU) in both these countries (Ortmann et al.
2015, Simmons 2015).
Numbers of Caspian Terns estimated to have bred
in different years at coastal sites in Angola, Namibia,
and South Africa from 1878–2022 are shown in Table 1. Caspian Terns nesting at Selley’s Lakes, Lake St Lucia, July 2017
Information was collated from Clinning (1978), Berruti (photo S Mfeka)

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