|Location||South Africa, Western Cape|
|Central coordinates||19o 25.00' East 34o 41.00' South|
|IBA criteria||A1, A4i, A4ii, A4iii|
|Altitude||0 - 9m|
|Year of IBA assessment||1998|
Summary Dyer Island is one of two low-lying islands situated 4.7 km southeast of Danger Point; the nearest harbour is at Kleinbaai/Franskraal, just south of Gansbaai. This flat, low- lying island does not exceed 9 m above sea level.
Site description Dyer Island is one of two low-lying islands situated 4.7 km south-east of Danger Point. The nearest harbour is at Kleinbaai/Franskraal, just south of Gansbaai. The coastline is rugged with some low rocky areas spreading inland. The island is flat and low-lying, with a pebbly surface. The vegetation consists primarily of Mesembryanthemaceae and non-native weeds (including conspicuous stands of Lavatera). In the south-eastern part of the island are several buildings that house the island staff, boats and stores.
Key Biodiversity See Box for key species. The discovery of Oceanodroma leucorhoa in several of the stone walls on the island in October 1995 was the first evidence of a procellariiform bird breeding in southern Africa. In November 1996 it was estimated that 8–9 pairs were breeding. In 1996, after an absence of some 25 years, Sterna dougallii, which breed regularly only at two other islands in southern Africa (Bird and St Croix islands in Algoa Bay; IBA ZA074), attempted to breed again at Dyer Island. The breeding attempt failed owing to suspected human disturbance. The population of Spheniscus demersus at Dyer Island is in rapid decline, and although the island supported some 72,500 birds in 1976, it is thought that the population may have fallen below 3,000 pairs in 1997.Many other species breed on this island, including large numbers of Phalacrocorax capensis and small numbers of P. carbo, P. neglectus and P. coronatus. Several large colonies of Larus hartlaubii and Sterna bergii breed at the island. Sterna sandvicensis, S. hirundo, S. paradisaea and S. vittata form large, mixed tern roosts with the breeding S. bergii. Dyer Island is estimated to hold over 1% of the world population of Haematopus moquini.
Non-bird biodiversity: The waters around the island hold a large population of the shark Carcharodon carcharias (VU).
|Species||Season||Period||Population estimate||Quality of estimate||IBA Criteria||IUCN Category|
|African Penguin Spheniscus demersus||resident||-||3,050 breeding pairs||-||A1, A4ii||Endangered|
|African Penguin Spheniscus demersus||winter||-||9,000 individuals||-||A1, A4ii||Endangered|
|Cape Cormorant Phalacrocorax capensis||resident||-||35,580 breeding pairs||-||A1, A4i||Endangered|
|Cape Cormorant Phalacrocorax capensis||winter||-||100,000 individuals||-||A1, A4i||Endangered|
|Bank Cormorant Phalacrocorax neglectus||breeding||-||uncommon||-||A1||Endangered|
|Crowned Cormorant Microcarbo coronatus||resident||-||60-238 breeding pairs||-||A1, A4i||Near Threatened|
|Crowned Cormorant Microcarbo coronatus||winter||-||150-500 individuals||-||A1, A4i||Near Threatened|
|African Oystercatcher Haematopus moquini||resident||2000||27-67 breeding pairs||unknown||A1, A4i||Near Threatened|
|African Oystercatcher Haematopus moquini||winter||-||160 individuals||-||A1, A4i||Near Threatened|
|Kelp Gull Larus dominicanus||breeding||-||88-130 breeding pairs||-||A4i||Least Concern|
|Kelp Gull Larus dominicanus||winter||-||200-500 individuals||-||A4i||Least Concern|
|Hartlaub's Gull Larus hartlaubii||breeding||-||110 breeding pairs||-||A4i||Least Concern|
|Hartlaub's Gull Larus hartlaubii||winter||-||280 individuals||-||A4i||Least Concern|
|Greater Crested Tern Thalasseus bergii||breeding||-||300 breeding pairs||-||A4i||Least Concern|
|Greater Crested Tern Thalasseus bergii||winter||-||750 individuals||-||A4i||Least Concern|
|A4iii Species group - seabirds||resident||-||100,000-499,999 individuals||unknown||A4iii|
|Medium - based upon reliable but incomplete / partially representative data|
|Biological resource use||fishing & harvesting aquatic resources - unintentional effects: large scale||happening now||small area/few individuals (<10%)||no or imperceptible deterioration||low|
|Biological resource use||fishing & harvesting aquatic resources - unintentional effects: subsistence/small scale||happening now||some of area/population (10-49%)||no or imperceptible deterioration||low|
|Climate change and severe weather||storms and floods||likely in short term (within 4 years)||some of area/population (10-49%)||moderate to rapid deterioration||medium|
|Human intrusions and disturbance||recreational activities||happening now||some of area/population (10-49%)||no or imperceptible deterioration||low|
|Human intrusions and disturbance||work and other activities||happening now||small area/few individuals (<10%)||no or imperceptible deterioration||low|
|Invasive & other problematic species, genes & diseases||invasive non-native/alien species/diseases - named species||happening now||some of area/population (10-49%)||no or imperceptible deterioration||low|
|Invasive & other problematic species, genes & diseases||problematic native species/diseases - named species||happening now||some of area/population (10-49%)||moderate to rapid deterioration||high|
|Pollution||garbage & solid waste||happening now||some of area/population (10-49%)||slow but significant deterioration||medium|
|Pollution||industrial & military effluents - oil spills||happening now||some of area/population (10-49%)||slow but significant deterioration||medium|
|Residential and commercial development||housing and urban areas||happening now||small area/few individuals (<10%)||no or imperceptible deterioration||low|
|Residential and commercial development||tourism and recreation areas||happening now||small area/few individuals (<10%)||no or imperceptible deterioration||low|
|Rocky areas||Scree, boulders & bare rock||0||0||moderate (70-90%)||good (> 90%)||near favourable|
|Whole area of site (>90%) covered by appropriate conservation designation||A comprehensive and appropriate management plan exists that aims to maintain or improve the populations of qualifying bird species||The conservation measures needed for the site are being comprehensively and effectively implemented||high|
Local conservation groups The local conservation group below is working to support conservation at this IBA.
|Dyer Island Conservation Trust||0|
|IUCN habitat||Habitat detail||Extent (% of site)|
|Rocky areas||Scree, boulders & bare rock||-|
|Land-use||Extent (% of site)|
|nature conservation and research||100%|
References Adams (1991), Branch (1991), Brooke and Prins (1986), Cooper (1981), Cooper and Berruti (1989), Cooper and Brooke (1986), Cooper et al. (1983, 1984), Crawford (1995), Crawford and Dyer (1995), Crawford and Shelton (1978, 1981), Crawford et al. (1982a,b, 1983, 1989, 1990, 1994, 1995c), Frost et al. (1976), Furness and Cooper (1982), Hockey (1983), Hockey and Hallinan (1981), Morant et al. (1981), Rand (1963), Randall and Randall (1980), Randall et al. (1980), Shelton et al. (1982), Siegfried (1982), Summers and Cooper (1977), Whittington (1996), Whittington and Dyer (1995), Whittington et al. (1998), Williams et al. (1990), Wilson et al. (1988).
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Recommended citation BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Dyer Island Nature Reserve. Downloaded from http://www.birdlife.org on 22/10/2016
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