Page 529 - Atlas Sea Birds Ver1

Stag and Bird (Algoa Bay) islands (Table 1). It may prove An expansion of Lüderitz Harbour in the late 1990s,
difficult to manage the Sandy Point fish factory, Cape consequent increased activities around the harbour, and
Town waterfront, and Danger Point Abalone Farm, but a simultaneous increase in the numbers of feral cats
consideration should be given to recognising the other (Felis catus) there may have displaced Greater Crested
15 sites as regional IBAs for the nominate race. Terns from Lüderitz Harbour and Shark Island to breed
at Penguin, Seal, and Halifax islands (Tom et al. 2024b).
Conservation issues Feral cats displaced Greater Crested Terns from breeding
at Robben Island in 1997 and 1998 (Crawford and Kroese
Trends in the overall population of T. b. bergii have been 2000). Greater Crested Terns were susceptible to an
largely driven by food abundance and availability. Hence, outbreak ofhighly pathogenic avian influenza (HPAI) in
sufficient forage and suitable breeding habitat near to the 2017 and 2018 (Khomenko et al. 2018).Then, of 7,560
prey resources are a sine qua non for the population. Nests wild birds infected or suspected to be infected by HPAI,
on islands in saltworks are vulnerable to changing water 5,363 were Greater Crested Terns and the disease killed
levels that may flood them or, by receding, increase their an estimated 1,700 chicks at a colony at Cape Town
accessibility to predators. Greater Crested Terns bred at waterfront (Roberts 2018). In 2003, 103 Greater Crested
Mile 4 Saltworks in 1986 (Williams 1987) but subsequently Terns that were incapacitated by marine foam (generated
the nature of the evaporation pans changed, they became by wave action, kelp mucilage, and phytoplankton) were
more flooded and there was no longer suitable habitat for rescued at Robben Island, of which 93 were released back
nesting (Tom et al. 2024a). to the wild after rehabilitation (Parsons et al. 2006).

Greater Crested tern colony at Dassen island (photo L Upfold)

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