Page 199 - Atlas Sea Birds Ver1

White- pusillus pusillus) annually killed 9% of the adult population
Bank Crowned Hartlaub's
Year breasted of African Penguins in the mid-1990s and 7% in the mid-
Cormorant Cormorant Gull
Cormorant 2000s (Marks et al. 1997, Makhado et al. 2013). However,
1976 26 22 when prey species shifted south and east at the recent turn
1977 25 27 of the century, there was a tendency for penguin colonies in
1979 113 7 11 northwest South Africa to decrease and those in the south-
1980 1 west to increase. The ongoing decrease at Dyer Island was
an exception to this pattern (Crawford et al. 2011). When
1996 0 the size of the penguin colony at Dyer Island was > 3,500
2006 0 0 pairs, numbers of penguins breeding there were negatively
2007 0 related to sardine catches made within 20 nautical miles of
2008 0 the island, suggesting an influence of local exploitation of
2009 0 prey species on the colony (Ludynia et al. 2014). In 2004,
2010 0 70,000 tonnes of sardine were caught within 20 nautical
2011 0 0 0 0 miles of Dyer Island (Ludynia et al. 2014) and in 2002 and
2012 0 0 0 from 2005–2007 the exploitation rate of sardine west of
2013 0 0 0 Cape Agulhas was 30–44% (Coetzee et al. 2008). In ad-
2014 0 0 0 dition to substantially depleting local availability of prey,
2015 0 0 0 the heavy fishing in the area may have caused sardine to
shift farther east (Coetzee et al. 2008), beyond the foraging
2016 0 0 0 range of African Penguins.
2017 0 0 0 0 Since 1978, Dyer Island has held large numbers of
2018 0 0 0 0 Cape Cormorants, almost 50,000 pairs in 1985. In the
2019 0 0 0 2010s, 54% of South Africa’s Cape Cormorants bred at
Dyer Island (Crawford et al. 2016). In 1956, the island had
Dyer Island a colony of c. 100 pairs of Bank Cormorants. In 2005, 30
Coordinates: 34.6818 S; 19.4190 E pairs bred at the island but this dwindled to just one pair
Description: A relatively flat island c. 20 ha in extent that in 2021.
rises to a height of c. 6 m. It has mixed vegetation over In 1996, 19 pairs of Leach’s Storm Petrel were found
a pebble-covered surface. Buildings at the northeast end breeding in dry stone walls around the island’s settlement,
housed staff, stores and boats (Rand 1963). Dry-stone which was the first record of the species breeding in the
walls were built around the settlement and there was southern hemisphere (Whittington et al. 1999). However,
a furnace to render seal blubber to oil. The island is still after 1998 numbers decreased and since 2005 no petrels
staffed and has a jetty near the buildings. were observed breeding at the island. Up to 108 pairs (in
Seabird guano was collected at Dyer Island in 76 years 2005) of White-breasted Cormorant, 266 pairs (in 2007) of
between 1896 and 1995, the total quantity removed from Crowned Cormorant, 610 pairs (in 2012) of Kelp Gull, 430
the island in that period being 14,060 metric tons (Tom et pairs (in 2014) of Hartlaub’s Gull, four pairs (in 1991) of
al. 2024). Grey-headed Gull, 6,722 pairs (in 2006) of Greater Crested
Between 1875 and 1941, 217,180 African Penguin Tern, 21 pairs (in 2012) of Caspian Tern and 47 pairs (in
eggs were harvested at the island (Makhado et al. 2024). 2020) of Roseate Tern have bred at the island, emphasis-
Conservation status: It was gazetted as the Dyer Island ing its importance for seabirds of the region. Great White
Provincial Nature Reserve in 1988 (Province of the Cape Pelicans bred in unknown numbers at Dyer Island in the
of Good Hope 1988) and is administered by CapeNature. 1800s and early 1900s, but persecution of pelicans by
Species and numbers breeding: Fourteen of the guano collectors caused then to abandon Dyer Island and
15 seabirds that breed in the BUS have bred or attempted move to Seal Island in False Bay after 1919 (Crawford et
to breed at Dyer Island, the exception being Damara Tern, al. 1995b).
which in South Africa has only been recorded nesting on
the mainland (Martin et al. 2024). Cape Gannets roosted at
Dyer Island in large numbers in 1984 (Berruti 1985) and did
so again in 1985, when a single nest with an abandoned
egg was found (Crawford et al. 1986). Known breeding
attempts and numbers breeding for the other 13 species
are shown on the following Dyer Island table.
About 4,000 pairs of African Penguin bred at the island
in 1958, which increased to > 22,000 pairs in 1979 (Rand
1963, Shelton et al. 1984) and remained above 18,000
pairs in 1986. The number breeding then decreased to
fewer than 2,000 pairs after 2006. In the late 20th century,
there was emigration of penguins fledged at Dyer Island to
colonies farther west (Crawford et al. 1995a, Whittington et
al. 2005). At Dyer Island, Cape Fur Seals (Arctocephalus A view of Dyer Island (photo L Upfold)

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