BIRD AREA
(reproduced)

Important Bird Areas of the Western Cape: Global IBA (A4i,iii) - 34/05'S; 18/31'E
False Bay Park - estimated 3000ha.

Site description:
This Important Bird Area (IBA) is centered on Strandfontein Sewage Works, but it also includes Zeekoeivlei and Rondevlei Nature Reserve, situated on the Cape Flats between Muizenberg and Mitchell's plain, 20k South of Cape Town, this IBA, like many Wetlands around South Africa's major cities is almost entirely human made. Prior to 1922 the only wetland habitat at the site was the small temporary marsh, Tamatievlei.

In 1922, a small sewage works was built and additional water was channeled into the system from the nearby Zeekoeivlei. Over the years the complex has been enlarged progressively. By 1976 the small marsh, Tamatievlei had been converted into 34 settling ponds covering over 306 ha.

The system provides a range of semi-natural habitats, including deep and shallow open water, seasonal open ponds, canals with aquatic vegetation, reed, rush and sedge beds, bare and vegetated shorelines and islands. Well-grassed banks separate the ponds. Several distinctive wetland plant communities occur, including perennial wetland, reed marsh and sedge marsh. The perennial wetland is characterised by scant aquatic vegetation dominated by Typha capensis, Phragmites spp., Scirpus spp., Potamogeton pectinatus, Lemna gibba, Myriophyllum aquaticum and Nasturtium spp., especially in the water canals. Typha capensis and Phragmites spp., dominate the reed beds. The reed marsh consists of virtually mono-specific stands of Phragmites australis, invaded in parts by Typha capensis.

The sedge marsh is quite diverse, but Bolboschoenus maritimus and Juncus kraussii dominate it.

The sewage works functions entirely by algal decomposition, a process that requires a large number of shallow vleis. The algae and the large number of copepods, which accompany them, provide a rich food supply for many bird species. Paspalum vaginatum, Pennisetum clandestinum and Zantedeschia aethiopica dominate the grasslands and small islands in the shallow open ponds, whereas Ammophila arenaria and Senecio spp., inhabit dunes and coastal areas.

The natural terrestrial strandveld surrounding the wetland consists of a scattered perennial overstorey of spinescent species, succulents and moderately tall evergreen thickets including Metalasia muricata, Phylica spp., and Chrysanthemoides monolifera. Annuals are conspicuous in the open areas in spring. The strandveld is heavily invaded in many areas by an alien woody overstorey consisting mainly of Acacia cyclops and A. saligna. The area is now largely surrounded by suburban development. The water levels in pans are manipulated, and are dropped in summer, resulting in temporal variability of water conditions.

The wetlands act as a network, but the majority of the birds are centered on the IBA, where a total of' 168 species has been recorded; of these, 76 are freshwater wetland species and a further 18 are coastal species that visit the area to roost or breed.

Breeding has been confirmed for 45 water bird species. This high diversity of water birds is due to the wide range of wetland habitats present, and the proximity of the IBA to the ocean which permits both freshwater and coastal species to exploit the system.

The abundance of water birds supported by this IBA has increased progressively since the 1950s reaching an average of over 23200 individuals during the period 1980 /1990. During extreme years, numbers are boosted above the 30000 limit.

The following threatened and near-threatened species are found at Strandfontein;

Greater Flamingo Phoenicopterus ruber,
Lesser Flamingo Phoeniconaias minor,
White Pelican Pelecanus onocrotalus,
African Marsh Harrier Circus ranivorus,
African Black Oystercatcher Haematopus moquini,
Caspian Tern Hydroprogne caspia,
and Chestnutbanded Plover Charadrius pallidus.

Strandfontein also occasionally holds globally significant numbers of;

Blacknecked Grebe Podiceps nigricollis,
Cape Cormorant Phalacrocorax capensis,
Southern Pochard Netta erythrophthalma,
Cape Shoveller Anas smithii,
Avocet Recurvirostra avosetta,
Hartlaub's Gull Larus hartlaubii,
Kelp Gull L. dominicanus and
White winged Tern Chlidonias leucopterus.

The site fields a regular tern roost of some 3000 birds when the water is low enough for islands to form in the shallow pans, including fairly large numbers of Common Sterna hirundo, Sandwich S. sandvicensis and Swift Tern S. bergii.

The IBA also occasionally holds regionally uncommon species such as the Great White Egret Casmerodius albus and Yellowbilled Egret Egretta intermedia. The surrounding alien Acacia and remaining strandveld vegetation holds Cape Francolin francolinus capensis and Cape Bulbul Pycnonotus capensis.

Other threatened/endemic wildlife:
Tile South African endemics, the Sand Toad Bufo augusticeps, Arum Lily Frog Hyperolius horstockii and Cape Dwarf Chameleon Bradypodion pumilum have been found nearby and may well be present in the IBA.

Conservation issues:
The IBA is administered by the Cape Town City Council. Concomitant with the increasing size of the sewage works. and the increase in diversity of aquatic habitats, has been the dramatic proliferation in numbers and diversity of water birds exploiting the complex.

In the 1950s, approximately 200 individuals comprising 12 species could be expected, whereas today thousands and tens of thousands of individual's of between 50 and 60 species of water bird are regularly counted at Strandfontein.

Numbers of Lesser Flamingo have decreased dramatically in the last decade This may be due to the introduction of Tilapia to the treatment ponds, which have changed the ecological character of the pans, reducing the abundance of small aquatic invertebrates, the Flamingos' favoured food item.

In 1986 there was a switch to chemically based sewage treatment in Cape Town. As a result the ponds are only used to treat sewage in emergencies and do not support as many birds as they did when sewage regularly passed through the system.

Nationally threatened
Breeding (pairs)
Total numbers
African Marsh Harrier
1-2
5 (av)-13 (max)
Caspian Tern
Br
11 (av)-27 (max)
Globally near-threatened    

Lesser Flamingo *

 
80 (avail 147 (max)
African Black Oystercatcher
Br?
22 (av)-46 (max)
Nationally near-threatened

White Pelican

195 (av)-346 (max)
Cape Cormorant
1000-15000
2665 (av)-4000 (max)

Greater Flamingo

1878 (avail 328 (max)

Peregrine Falcon

OV

Lanner Falcon

OV

Chestnutbanded Plover

OV
RR & BRA
Status
Cape Francolin
Common
Cape Bulbul
Common
 
Breeding (pairs)
Total numbers
1% or more of population  
Great Crested Grebe
Br
25 (av)-51 (max)
Blacknecked Grebe
Br
328 (av)-1 380 (max)
Dabchick
Br
403 (av)-628 (max)
Cape Cormorant
Br
2665 (av)-40000 (max)

South African Shelduck

87 (av)-477 (max)
Cape Teal
Br
468 (avail 1799 (max)
Cape Shoveller
Br
603 (av)-1418 (max)
Southern Pochard
Br
346 (avail 1332 (max)

Avocet

467 (av)-942 (max)
Kelp Gull
Br
996 (avail 3685 (max)
Hartlaub's Gull
Br
1156 (avail 3506 (max)

Swift Tern

 
0-753 (max)

Sandwich Tern

 
0-3027 (max)

Whitewinged Tern

 
1025 (avail 6832 (max)

0.5% or more of population  
Maccoa Duck
Br
64 (av)-379 (max)
 

Other Important populations  
Yellowbilled Duck
Br
133 (av)-519 (max)

* - Species both globally and nationally threatened  
^ - Species does not meet IBA threshold  
F - Number of females (for polygamous species)  
group - Number of groups (for co-operative breeders)  
RR & BRA - Restricted-range and biome-restricted assemblage  
av - Yearly average (max count)  
max - Absolute maximum
BP? - Suspected breeding    
OV - Occasional Visitor    
Br - Confirmed breeding    
V - Vagrant    

Birds that breed at the nearby Rondevlei Nature Reserve, currently the only protected vlei on the Cape Flats, probably forage extensively at the sewage works. During the 1980s a coastal Park, which linked the Strandfontein Sewage Works to Rondevlei and Zeekoeivlei was proposed. The proposed Park was never realized, owing, to a money shortage.

Newly proposed developments in the area, which would isolate Rondevlei and Zeekoeivlei, have led to renewed calls for the establishment of a reserve protecting these important wetlands and their surrounding endangered strandveld vegetation, which is under threat from invasive alien Acacia saligna and a. cyclops.

Being within the vicinity of Cape Town, Strandfontein is an ideal, easily accessible environment for bird watching based ecotourism and appropriate facilities to exploit this potential should be developed.

The wetland's proximity to the Cape Flats region provides further incentive to create economic returns for the communities living close to the IBA. Furthermore, Strandfontein could fulfil useful Educational and Scientific functions.

The accessibility of this artificial wetland, and the range of habitats and associated fauna and flora present, give it great educational potential.

The water regime at Strandfontein is unique in comparison with the majority of important South African wetlands, in that people regulate it. This creates slightly different foraging conditions for birds, especially those that feed on benthic invertebrates.

Immediate attention should be given to the fact that several bird species of conservation interest (e.g. Caspian Tern) ceased breeding in the area or show irregular breeding patterns. The commonest causes of low breeding success or breeding failure in water birds have usually been attributed to changes in water level.

The management plan should promote the development of suitable breeding sites for these species, including the the creation of islands in the pans and the manipulation of water levels to prevent flooding of the existing breeding sites.

Improved breeding activities of some water birds, however, have been observed at Strandfontein in the last decade, and are believed to be due to improved water quality in the pans.

Further reading:
Allan et al. (1990); Ashkenazi (1986); Berruti & Sinclair (1983); Broekhuisen & Frost (1968); Chittenden (1992); Cooper & Pringle (1977); Cooper et al. (1976); Kalejta-Summers et al. (in press b); Longrigg (1982); Ryan et al. (1988); Schneider (1990); Summers et al. (1977); Turpie (1995); Underhill & Cooper (1984); Winterbottom (1960, 1968c).

 

 

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