Page 244 - Atlas Sea Birds Ver1

2.2.4.12 Breeding by seabirds at islands in Algoa Bay

Authors: RJM Crawford, BM Dyer, L Pichegru, RM Randall, BM Randall, PA Whittington, M Masotla, and AB Makhado

Abstract:
Eight seabird species have bred at six islands in Algoa Bay in South Africa’s Eastern Cape Province, which lies at the eastern boundary
of the Benguela Current ecosystem: African Penguin (Spheniscus demersus), Cape Gannet (Morus capensis), Cape Cormorant (Phala-
crocorax capensis), White-breasted Cormorant (P. lucidus), Kelp Gull (Larus dominicanus), Greater Crested Tern (Thalasseus bergii),
Caspian Tern (Hydroprogne caspia) and Roseate Tern (Sterna dougallii). The islands are the easternmost breeding localities of African
Penguin, Cape Gannet, Cape Cormorant and the nominate race of Greater Crested Tern, although there is a single 1920s record of Cape
Cormorant breeding farther east. In southern Africa, there are only three records of Kelp Gull breeding farther east. The islands also com-
prise the most eastern breeding localities for Roseate Tern in South Africa. Since 1990, Bird Island has supported the largest of six extant
colonies of Cape Gannet and in 2018 it held 71% of the global population of this species. St Croix Island held > 19,000 pairs of African
Penguin in 1985 and 1993. Islands in Algoa Bay had > 20,000 pairs of African Penguin in the 1990s and early 2000s, but this decreased
to < 10,000 pairs in 2016 and < 3,000 pairs in 2022. Since the 1970s Algoa Bay’s islands supported most of South Africa’s population of
Roseate Tern, with a maximum of 300 pairs in 2010 and a 2019 count of 180 pairs.
Introduction:
Eight seabird species have bred at six islands in Algoa Bay in South Africa’s Eastern Cape Province: African Penguin (Spheniscus demer-
sus), Cape Gannet (Morus capensis), Cape Cormorant (Phalacrocorax capensis), White-breasted Cormorant (P. lucidus), Kelp Gull (Larus
dominicanus), Greater Crested Tern (Thalasseus bergii), Caspian Tern (Hydroprogne caspia) and Roseate Tern (Sterna dougallii) (Craw-
ford et al. 2009). The islands occur in two groups: St Croix Island group (Jahleel, Brenton and St Croix) in the west and Bird Island group
(Black Rocks, Seal, Stag and Bird) in the east (Figure 1). Black Rocks supports a herd of Cape Fur Seals (Arctocephalus pusillus pusillus)
(Seakamela et al. 2024) but is low-lying, sometimes awash and has not been used by seabirds for nesting. The islands comprise the
eastern-most breeding localities of African Penguin, Cape Gannet and Cape Cormorant and of the nominate race of Greater Crested
Tern (T. b. bergii), although there was a record of Cape Cormorant breeding farther east in the 1920s (Cooper et al. 1982). The islands
also are the most eastern breeding localities for Roseate Tern in southern Africa (Randall and Randall 1980). However, to the east White-
breasted Cormorant and Caspian Tern breed coastally in substantial numbers, including at Lake St Lucia in northern KwaZulu-Natal (Fox
et al. 2024).
Hartlaub’s Gull (Chroicocephalus hartlaubii), Grey-headed Gull (C. cirrocephalus) and Damara Tern (Sterna dougallii) have bred along
the Algoa Bay coastline, which is the most eastern limit of breeding by Hartlaub’s Gull and Damara Tern (Martin and Whittington 2024).
However, Grey-headed Gull also breeds at Lake St Lucia, as does Great White Pelican (Pelecanus onocrotalus) (Fox et al. 2024). Great
White Pelican has visited Bird Island (RJMC, BMD unpublished observations) but has not been known to breed there. In southern Africa,
there are three records of 1–2 pairs of Kelp Gull breeding east of, but within c. 100 km of, Woody Cape at the east of Algoa Bay (Whit-
tington and Crawford 2024). Therefore, the neighbourhood of Woody Cape bounds the breeding distribution of eight of the 15 seabirds
that breed in the Benguela upwelling ecosystem. It also is regarded as the eastern boundary of that system (Makhado et al. 2021). The
four Benguela seabirds that breed farther east also breed at inland waterbodies (Hockey et al. 2005).
With regard to the other three seabirds that breed in the Benguela system, Bank Cormorant (P. neglectus) has done so only west of
Cape Agulhas, which lies at the junction of the Atlantic and Indian oceans (Cooper 1981). This has also been the case for most Crowned
Cormorants (Microcarbo coronatus) (Crawford et al. 2012), although in 2003 a few bred in Tsitsikamma National Park thereby extending
their breeding range c. 355 km to the east (Whittington 2004). Crowned Cormorant has been seen at Bird Island, but has not bred there
(Crawford et al. 2008). Leach’s Storm Petrel (Hydrobates leucorous or Oceanodroma leucorhoa) is a common summer visitor from the
northern hemisphere to southern African waters and has bred in small numbers in South Africa’s Western Cape (Whittington et al. 1999).
It occurred seasonally at St Croix Island (Randall and Randall 1986) and may have bred there (Underhill et al. 2002).
From the early 1890s the Algoa Bay islands were administered by the government of the Cape Colony (Shaughnessy 1984). The
Union of South Africa came into existence in 1910 and the islands then fell under that government’s Guano Islands division. Black Rocks
and Seal, Stag and Bird islands were gazetted as provincial nature reserves in 1988 (Province of the Cape of Good Hope 1988). In 1998,
the Algoa Bay Island Nature Reserve, which then included all six islands and Black Rocks, was recognised as a globally Important Bird
and Biodiversity Area (IBA). At that time, it held substantial proportions of the overall populations of African Penguin and Cape Gannet
and most of South Africa’s Roseate Terns (Barnes 1998). In 1985 and 1993, > 19,000 pairs of African Penguins nested at St Croix Island
(Crawford et al. 2013), but that fell to only 2,262 pairs in 2022. Islands in Algoa Bay had > 20,000 pairs of African Penguin in the 1990s and
early 2000s, but that decreased to < 10,000 pairs in 2016 and < 3,000 pairs in 2022. Likely drivers of these decreases included competi-
tion with purse-seine fisheries for food (Pichegru et al. 2010, 2012) and ship to ship bunkering near colonies (Sherley et al. 2020). Seismic
surveys too may have had adverse impacts on penguins (Pichegru et al. 2017). After 1990 Bird Island supported the largest of six extant
colonies of Cape Gannet and in 2018 it held 71% of the global population of this species (Sherley et al. 2019). Since the 1970s Algoa
Bay’s islands have supported most of South Africa’s population of Roseate Tern (Crawford et al. 2009), with a maximum of 300 pairs in
2010 and >200 pairs in 2022 (Crawford et al. 2024). In winter, the Bird Island group held large numbers of Antarctic Terns (Barnes 1998).
In 2005, the Algoa Bay islands were incorporated into the Greater Addo Elephant National Park (GAENP) and in 2015 they were again
considered to be a globally important IBA (Marnewick et al. 2015). In 2019, a marine protected area around the islands was proclaimed.
The six islands at which seabirds have bred in Algoa Bay are briefly described below. For each island records of breeding by the differ-
ent species were collated for all years having information. When multiple counts were obtained for a species in a given year, the maximum
was shown on the relevant table. ‘√’ signifies that breeding occurred at a locality but the numbers were not ascertained; ‘?’ that breeding
may have taken place. A short summary of methods used to obtain the estimates of numbers breeding is given in the chapter ‘Introduction
to Seabird Breeding Localities’.

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