Page 319 - Atlas Sea Birds Ver1

heavy fishing of sardine in its vicinity: 70,000 tonnes of
sardine were caught within 30 km of Dyer Island in 2004
(Ludynia et al. 2014). When the colony size at Dyer Island
was > 3,500 pairs, numbers of penguins breeding there
were negatively related to sardine catches made within 20
nautical miles of the island (Ludynia et al. 2014).
In 2015, African Penguins were considered Endangered
(EN) in both Namibia (Kemper 2015) and South Africa
(Hagen 2015). Generation length (G) for birds is defined
as: G = A + (1/(1 − ϕ )), where A is age at first breeding
a
and ϕ is annual survival of adults (Birdlife International
a
2000). For African Penguins, A can vary from four to six
years depending on food availability (Crawford et al.
1999, Whittington et al. 2005). When food is reasonably
abundant ϕ is about 0.81 or 0.82 p.a. (Crawford et al.
a
A newly hatched African Penguin chick (photo L Upfold) 1999, Whittington 2002, Sherley et al. 2014). Based
on these values Sherley et al. (2020) calculated G = 10
Recife in 1981, which was the only record for that site years for African Penguins. They used a Bayesian state-
(Every 1983). Thirteen of the 39 colonies were extinct by space model to assess the conservation status of African
2022: Seal, North Long, North Reef, and Albatross islands Penguins and concluded that it met the threshold for
in Namibia; Bird (Lambert’s Bay), Jacob’s Reef, Marcus, classification as EN with a high (97%) probability. In 2022,
Geyser, Quoin Rock, Seal (Mossel Bay), Brenton, and Stag the conservation status of African Penguins was listed by
islands and the Cape Recife site in South Africa. the International Union for Conservation of Nature (IUCN)
The overall population of African Penguins was about as EN because it was undergoing a very rapid population
141,000 pairs in 1956 (Rand 1963a, b, Crawford et al. decline ‘probably as a result of commercial fisheries and
2001), 51,500 pairs in 1989 (Sherley et al. 2020), 56,000 shifts in prey populations’, and the trend showed no sign of
pairs from 1991–1994 (Crawford et al. 1995), 36,000 pairs reversing (BirdLife International 2022).
in 2007 (Kemper et al. 2007), 17,700 pairs in 2019 (Sherley
et al. 2020), and 14,800 pairs in 2020–2022 (Table 2). The Important Bird and Biodiversity Areas and threats
sum of the most recent counts made at breeding sites
was c. 13,250 pairs, of which only 0.44% was attributable Important Bird and Biodiversity Areas (IBAs) are identified
to values obtained before 2000 (Table 2). Therefore, the through the use of specific criteria. Criterion A1 is that
population has decreased by 90% since 1956. In Namibia, ‘the site is known or thought regularly to hold significant
numbers decreased by 91% from about 42,000 in 1956 to numbers of a Globally Threatened species’ (BirdLife
3,600 in 2020–2022; in South Africa they dropped by 89% International 2020). Guidelines for the application of IBA
from 99,000 in 1956 to 11,200 in 2020–2022. criteria recommend that to meet A1 a site must support at
Large decreases of African Penguins at colonies least 15 individuals (the equivalent of 5 Pairs/Reproductive
between Lüderitz in Namibia and Dassen Island off Units) of a species classified as EN (BirdLife International
west South Africa from the 1960s to the 1980s followed 2020). Twenty of the 26 colonies extant in 2022 held
collapses of sardine stocks off Namibia and South Africa more than five pairs and therefore should be regarded
(Crawford and Shelton 1978, Shelton et al. 1984, Crawford as IBAs (Table 2). The largest Namibian colony was at
2007). North of Lüderitz, increases at Mercury and Ichaboe Mercury Island, which had 1,826 pairs or 51% of Namibia’s
islands after the 1960s probably resulted from an increased population. In South Africa, Dassen Island then had most
local abundance of bearded goby (Crawford et al. 1985, pairs, 2,513 or 22% of its population. In 2022, six other
2001). From 1989–2009 numbers of penguins breeding colonies held > 800 pairs: Robben, Dyer, St Croix, and Bird
along west South Africa were significantly correlated with (Algoa Bay) islands and the mainland colonies of Simon’s
the overall biomass of sardine and anchovy in South Town and Stony Point. Given increased Allee effects as
Africa, as also was the case from 1999–2009 in Algoa Bay
(Crawford et al. 2011). New penguin colonies were formed
at Stony Point and Boulders on South Africa’s mainland
and at Robben Island. The formation of, and increases at,
these colonies and at Dassen Island, took place during a
period of recovery of South Africa’s sardine in the 1980s
and 1990s, and an increase in the biomass of anchovy at
the start of the 21 century (Underhill et al. 2006). After
st
2004, large decreases in numbers of penguins breeding in
west South Africa were associated with a shift to the south
and east of adult anchovy and sardine, and a collapse of
sardine (Crawford et al. 2011). By contrast, in the south,
numbers increased or stabilized at Boulders and Stony
Point and penguins attempted to form a new colony at
Witklippunt in De Hoop Nature Reserve (Underhill et al.
2006). However, at the southern colony of Dyer Island
penguins decreased in the 2000s, probably as a result of African Penguin chicks at Bird Island, Algoa Bay (photo L Upfold)

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