Page 169 - Atlas Sea Birds Ver1

between 1989 and 1992 in Crawford et al. (1984). Breeding
by Kelp Gulls was better synchronised in particular areas
than between different areas of the island (Crawford et
al.1984).
Seabird guano was collected at Dassen Island in
73 years between 1897 and 1975, the total quantity
removed from the island in that time being 24,006 metric
tons (Tom et al. 2024).
Between 1871 and 1967 at least (data were not available
for 23 years) 16,311,590 African Penguin eggs were
collected at Dassen Island (Makhado et al. 2024). A low
wall, completed by about 1942, was built around Dassen
Island about 100 m from the shoreline to restrict penguins
to the area outside the wall and thereby facilitate egg
collections (Crawford et al. 2007b). Concrete nests were
made for the penguins at the southwest of the island in
a further attempt to concentrate breeding pairs (Randall A view of Meeuwrots (photo L Upfold)
1989). The concrete nests were seldom used after 1978,
so appear not to be favoured nesting sites. Openings were recovered to 25,000 pairs in 2004 (Crawford et al. 2013a),
made in the exclusion wall in 1991 to allow penguins again before collapsing to about 2,500 pairs in 2022. The de-
to access and breed at the interior of the island (Crawford crease of penguins in the 1970s and their increase at the
et al. 2007b). recent turn of the century were attributed to reduced and
Excavations showed that Cape Fur Seals (Arctocepha- then improved availability of food (Crawford et al. 2001,
lus pusillus pusillus) formerly bred at West Bay (DFFE un- Underhill et al. 2006). The increase in the early 2000s oc-
published records) and a few pups were born in the south- curred despite a large number of penguins at the island
west in 2022 (Seakamela et al 2024). being oiled, or translocated to prevent their becoming oiled,
Conservation status: Dassen Island Provincial Nature after the Treasure oil spill between Dassen and Robben
Reserve was established in terms of Section 6 of the Na- islands in 2000 (Crawford et al. 2000). The decrease in
ture Conservation Ordinance (Ordinance 19 of 1974) on numbers of penguins at the island after the mid-2000s
9 March 1988 by Proclamation No. 23/1988 in the Provin- was attributed to a shift in the distribution of their main
cial Gazette of 18 March 1988 (Province of the Cape of prey, sardine (Sardinops sagax) and anchovy (Engraulis
Good Hope 1988). Its boundaries were amended by the encrasicolus), to the southeast and intense competition
extension of the area of jurisdiction to 500 m seawards with fisheries for those prey that remained in the west
of the high-water mark in terms of Section 6(1)(b) of the (Crawford et al. 2011). The reduced availability of prey was
Nature Conservation Ordinance (Ordinance 19 of 1974), associated with decreased survival of adult penguins at
read with Sections 2 and 5(1) of the Sea Shore Act, 1935. the island (Sherley et al. 2014). Reproductive success and
The amendment was effected by Provincial Notice 5/1999 adult survival of African Penguins at Dassen Island were
in the Provincial Gazette of 22 January 1999. Dassen significantly related to both the biomass of sardine and
Island Nature Reserve, including its marine component, anchovy and its availability to seabirds (Cury et al. 2011,
was designated as a marine Ramsar site on 29 March Crawford et al. 2019, 2022). Further studies concluded
2019 (Ramsar Reference number 2383). The island is that fisheries operating near African Penguin breeding
administered by the Western Cape Nature Conservation colonies compete with the birds for food, are detrimental to
Board, CapeNature. the penguin’s population health and are impeding recovery
Species and numbers breeding: Eleven seabird species of its population (Sydeman et al. 2021).
have bred at Dassen Island. Numbers of pairs to have done Leach’s Storm Petrel was first seen breeding at Das-
so are shown on Table 1. sen Island in the austral summer of 1997/98 (Crawford
African Penguins were first reported at Dassen Island in et al. 2007c), soon after it was first recorded breeding in
1601 (Shelton et al. 1984). Based on appraisals of the area the southern hemisphere at Dyer Island, South Africa in
used for their breeding (following maps in Kearton 1931) 1995/96 (Whittington et al. 1999). The largest number
and of the densities of nests, it was estimated that close to observed at Dassen Island was six pairs in 2020. In 2022,
one million pairs bred at the island in the 1920s (Crawford Dassen Island was the only known breeding locality for
et al. 2007b). A population model suggested that Dassen Leach’s Storm Petrels in southern Africa.
Island held 1.45 million African Penguins aged two years or Great White Pelicans started to breed at Dassen Island
older in 1910, 0.22 million in 1956 and 0.14 million in 1967, about 1956 after they were displaced from Seal Island
so that numbers of adult-plumaged penguins decreased in False Bay by loss of breeding habitat and disturbance
by 90% over that 57-year period (Shannon and Crawford caused by sealing activities there (Rand 1963, Crawford et
1999). The massive decrease was attributed to over- al. 1995a). Numbers breeding at Dassen Island increased
exploitation of the African Penguin’s eggs, which were prob- to a peak of 834 pairs in 2004 but then decreased to be-
ably commercially harvested at a rate of 48% of those pro- tween 250 and 500 pairs after 2008. The increase may
duced (Shannon and Crawford 1999). Aerial photographs have resulted from increased availability to the pelicans of
taken in 1956 suggested a breeding population then of offal at nearby pig farms (Crawford et al. 1995a) and the
c. 145,000 individuals (Rand 1963) or 72,500 pairs. In 1972, decrease from a subsequent reduction of offal.
penguins occupied about 70,000 nesting burrows (Frost More than 48,000 pairs of Cape Cormorants bred at the
et al. 1976). However, the number breeding decreased to island in 1988 but since that date annual numbers have
about 12,700 pairs in 1979 and 9,000 pairs in 1981. It then been fewer than 10,000 pairs. The largest number of Bank

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