Page 379 - Atlas Sea Birds Ver1

Longevity of at least 16 years has been recorded (Underhill < 100 pairs. Two sites, Schaapen Island and Robbesteen,
et al. 1999). Use of these parameters gave G ≥ 7.5 years each had a maximum of just one pair. The sum of maxima
and 3 G ≥ 22.5 years. Hence, the decrease over 42 years at all sites was 11,544 pairs (Table 3). This could be used
equated to ≥ 43% in 3 G and was within the 30–50% as an approximate carrying capacity of the Benguela
range of IUCN’s Red List criterion A2 for classification as ecosystem for the species. Of this, 45% was contributed
Vulnerable (VU, IUCN 2022). by Ichaboe Island and 22% by Mercury Island, and 79%
In Namibia, numbers of Bank Cormorants decreased by Namibia and 21% by South Africa. In 2020–2022,
by 84% from 7,166 pairs in 1978–1980 (Crawford et al. numbers in Namibia and South Africa were at 13% and
1999) to 1,182 pairs in 2018–2022 (Table 2). In South 23% of their respective carrying capacities.
Africa, they decreased by 63% from 1,506 pairs (Crawford By 2022, breeding had ceased at 18 of the 59 known
et al. 1999) to 560 pairs over the same period (Table 2). breeding sites (Table 2), so that only 41 colonies remained
These decreases amounted to ≥ 45% in 3G in Namibia and extant. At colonies monitored annually, extinctions
≥ 34% in 3G in South Africa and both met IUCN’s Red List occurred at Lambert’s Bay within 10 years of its holding
criterion A2 for classification as VU. 33 pairs, at Marcus Island six years after it had 35 pairs
In 2015, Bank Cormorants were classified as and at Jutten Island 11 years after it numbered 27 pairs
Endangered (EN) in Namibia (Roux and Kemper 2015) (Table 1). Therefore, every effort should be made to avoid
and in South Africa (Cook 2015). In 2022, they were reductions of colonies to below c. 50 pairs and to grow
classified as EN by BirdLife International (2022). smaller colonies above that level, for example through
the provision of additional nesting space.
Important Bird and Biodiversity Areas
Conservation issues
Important Bird and Biodiversity Areas (IBAs) are identified
through the use of specific criteria. Criterion A1 is that Threats to Bank Cormorants include loss of breeding habitat
‘the site is known or thought regularly to hold significant as a result of human disturbance (Crawford et al. 1999,
numbers of a Globally Threatened species’ (BirdLife 2018) or displacement by Cape Fur Seals (Arctocephalus
International 2020). Guidelines for the application of IBA pusillus pusillus, Crawford et al. 1989); competition with
criteria recommend that, to meet A1, ‘a site must support: at fisheries for prey species near breeding colonies (Sherley
least 30 individuals (the equivalent of 10 Pairs/Reproductive et al. 2017); and potential impacts of climate change, such
Units) of a VU species with a global population of > 1,500 as reduced breeding success caused by an increased
individuals …’’ (BirdLife International 2020). In view of this, loss of nests to storms or abandonment of nests on account
and given that the species’ population is > 1,500 individuals, of heat waves (Sherley et al. 2012), and displacement
should the Bank Cormorant be reclassified as VU, all sites of prey away from breeding sites (Crawford et al. 2008).
holding ≥ 10 pairs would qualify as IBAs. There are 11 such Additionally, oil spills around colonies may kill adult
sites in Namibia and 15 in South Africa (Table 2). Based birds, which are difficult to catch for rehabilitation (Crawford
upon the most recent counts made at colonies, 10 sites et al. 2000).
in Namibia and 11 in South Africa had ≥ 1% of the overall In order to mitigate these risks, spatial planning should
population (Table 2). The largest colonies were at Mercury target effective management at and around breeding sites
Island (54% of the overall population), Groot Paternoster with priority being given to larger colonies. Adult Bank
Rocks (5%) and Ichaboe Island (3%). Cormorants often remain within 10 km of breeding sites
The biggest Bank Cormorant colony to have been (Cooper 1985) but have moved 63 km between colonies
observed was 5,182 pairs at Ichaboe Island in 1993. In (Crawford et al. 1999). Young birds disperse more widely
2020–2022, the global population was just 34% of that (Cooper 1981). Bank Cormorants are benthic feeders and
amount. The only other site that supported > 1,000 pairs at Mercury Island foraged within c. 3 km of the colony
was Mercury Island. The maxima observed for twelve sites (Ludynia et al. 2010).
were from 100–362 pairs and 45 sites had a maximum The Namibian Islands Marine Protected Area restricts
access to and controls activities at most breeding sites of
Bank Cormorants in Namibia (Ludynia et al. 2012). However,
consideration should also be given to implementing
shipping routes that minimise the risk of oil washing ashore
at key colonies, staffing such sites to avoid their being
colonised by seals with resultant loss of breeding habitat
(as occurred in the late 20 century, Crawford et al. 1989),
th
and excluding fishing of prey species around them. In a
Bayesian state-space model, Bank Cormorant numbers
responded positively to an increased availability of Cape
rock lobsters (Jasus lalandii), a main prey item in South
Africa (Dyer et al. 2019), within 20–30 km of two South
African colonies, so that precautionary implementation of
closures to rock lobster fishing around important colonies
Bank Cormorant on a nest (photo L Upfold) was recommended (Sherley et al. 2017).

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