Page 539 - Atlas Sea Birds Ver1

For example, the most recent, known count at Pelican there is considered unsuitable for breeding by this species
Point was four pairs in 1964 and at Sandwich Harbour (Tom et al. 2024).
one pair in 1977. Therefore, the years of the most recent
counts at colonies are shown in Table 2, as well as the Conservation issues
percent contributions of counts made in different periods In southern Africa, mainland colonies of Caspian Tern were
to the sum of most recent counts. For example, the five sometimes susceptible to predation and disturbance by
pairs recorded at Pelican Point and Sandwich Harbour in feral dogs, Black-backed Jackals (Canis mesomelas) and
1964 and 1988 contributed c. 1% of the sum (397 pairs) of humans, decreasing their breeding success (Clinning 1978,
the most recent counts from all coastal sites. Counts made Berruti 1980, Martin and Randall 1987, Kemper et al. 2007,
in the 2000s contributed c. 41% of the most recent total Simmons 2015). In recent years, one or two pairs of Caspian
and counts in the 2010s/20s 58% (Table 2). In 2007, the Tern attempted to breed every year at Mile 4 Saltworks,
coastal population was thought to be 425 pairs (Kemper Swakopmund, but the eggs/chicks were predated. In
et al. 2007). 2019, 51 pairs established nests simultaneously and laid
In Sweden, Caspian Terns first visited colonies when eggs. However, the whole breeding attempt was wiped
2–3 years old but most bred from 6 years old. Survival out by Black-backed Jackals on two consecutive nights
in their first year was 60%, in their second year 85% and (Tom et al. 2024). In southern Africa, Caspian Terns have
thereafter 83% (Cramp 1985 in Tree 2005). From 1983– been entangled in fishing lines or caught by fishing hooks
1991, Caspian Terns at Swartkops River Estuary fledged (Cooper et al. 1992).
on average 0.7 chicks per pair (Tree 2005). Changes in Nests on islands in dams, salt works, and lakes are
these parameters would likely influence fluctuations in vulnerable to changing water levels that may flood them
numbers breeding, through advancing or deferring age at or, by receding, increase their accessibility to predators
first breeding and affecting recruitment into and mortality (Ortmann et al. 2015, Simmons 2015).Changes in water
from the breeding population. levels may be caused by natural events, including floods
Adding 45 inland pairs (Cooper et al. 1992) to the sum of and droughts, and management practices. In four breeding
maxima obtained at coastal colonies from 2018–2022 (319 seasons, flooding at Lake St Lucia caused very low
pairs) suggests a recent overall southern African population breeding success (Cooper et al 1992). Caspian Terns bred
of c. 364 pairs, or 728 mature individuals. Adding 45 pairs on sand banks and sand islands in the Orange River Estuary
to the sum of the most recent values recorded at coastal in 1980 and 1981 (Cooper et al. 1992), but they have not
sites (397 pairs) indicates a southern African population of been recorded to breed there subsequently (Crawford
c. 442 pairs, or 884 mature individuals. Both these values et al. 2018). In the 1980s, the Orange River Estuary lost
are lower than those of 501 pairs from 1980–1991 (Cooper 276 ha of its wetland area near the mouth as a result of
et al. 1992) and 551 pairs in 2015 (AEWA 2015). However, poor management practices (Bornman and Adams 2010),
recent numbers breeding inland have not been accurately which included altered river flow and artificial opening of
gauged. If the overall number breeding in southern Africa the mouth that led to reduced flooding of low-lying areas.
is < 500 pairs, the southern Africa Caspian Tern population These changes, and increased disturbance by humans,
should be classified as VU in terms of IUCN’s criterion D1 reduced the availability of suitable roosting and nesting
(number of mature individuals < 1,000; IUCN 2022). sites for birds (Anderson et al. 2003) and contributed to the
cessation of breeding in the estuary by Caspian Terns and
Important Bird and Biodiversity Areas other seabirds (Crawford et al. 2018). The last time that
Caspian Terns nested in the Swartkops Valley was in 2016.
In this valley, pumping operations ceased at Bar None
Important Bird and Biodiversity Areas (IBAs) are identified Saltpans from 2017 and at Redhouse Saltpans from 2018
through the use of specific criteria. Criterion A1 is that and the pans dried out, so that no suitable breeding habitat
‘the site is known or thought regularly to hold significant remained (Martin and Whittington 2024). In these ways
numbers of a Globally Threatened species’ (BirdLife management practices resulted in cessation of breeding
International 2020). Guidelines for the application of IBA at two of the seven coastal regions in southern Africa that
criteria recommend that to meet A1 ‘a site must support: formerly held > 10 breeding pairs of Caspian Terns and
at least 30 individuals (the equivalent of 10 Pairs/ would have met IBA requirements for a VU population.
Reproductive Units) of a species classified as Vulnerable’ Housing development at Die Dam may have rendered that
(BirdLife International 2020). Then, if the southern African site too disturbed for Caspian Terns to breed successfully.
population is considered VU, Ilha dos Tigres, Walvis Bay Caspian Terns in southern Africa feed on a variety of
Saltworks, Velddrif Saltworks, Lower Berg River, WCNP fish species (Tree 2005). Factors influencing the availability
including Caspian Island, Dyer Island, and Lake St Lucia of forage resources, such as the drying of waterbodies,
may qualify as IBAs for southern Africa’s Caspian Tern may influence the distribution and demography of Caspian
population (Table 2). Most recently Lake St Lucia held Terns. Seabirds at coastal sites in southern Africa, including
c. 40% of this population. Although in 2019 51 pairs of some at which Caspian Terns bred, have been susceptible
Caspian Terns established nests at Mile 4 Saltworks, north to outbreaks of disease such as highly pathogenic avian
of Swakopmund, they were unsuccessful and the habitat influenza (HPAI, Khomenko et al. 2018).

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