Department of Statistical Sciences
University of Cape Town
| Avian Demography Unit
Department of Statistical Sciences University of Cape Town |
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Location of the Bot River and Kleinmond estuaries
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Photo © Doug Harebottle Aerial view looking eastwards over the estuary (24 May 2001). |
| Map |
Map of the Bot River Estuary showing the extent of the wetland and the area covered for CWAC (in blue). Modified from Koop et al. 1982 (Estuaries of the Cape. Part II: Synopses of available information on individual systems. Report no. 18: Bot/Kleinmond system. CSIR Research Report 417) |
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| Description | The Bot River Estuary, or Botriviervlei as it is more commonly known, is one of the largest estuarine systems in the Western Cape, covering an area of approximately 14 km2 when fully inundated. It is joined to the nearby Kleinmond estuary by a narrow channel called "Die Keel" and together these two areas make up the Botrivervlei/Kleinmond IBA (SA118). Both systems are counted for CWAC. Major habitats include river, open water, shoreline, mud- & sandflats (during low water levels), marsh (around Die Keel) and reedbeds (mainly Phragmites and Scirpus). Other aquatic plants that occur include two species of water weed - Ruppia maritma (dominant) and Potamogeton pectinatus. The surrounding land is mostly privately owned and the estuary is a well-known recreational venue for boating, skiing and windsurfing. | ||
| Ecology | Historically, the estuary was open to the sea but since the mid-1800s a large dune barrier dammed the mouth, near Sonesta, and the estuary changed to a semi-permanent closed system. Natural breachings take place sporadically when heavy rainfall in the catchment raises water levels in the estuary breaking the dune barrier and opening the mouth to the sea. Artficial breachings also occur and have resulted mainly from local fisherman wanting to replenish marine fish stocks. These artificial breachings, which also occur at the Kleinmond estuary, occur sporadically and result in dramatic drop in water levels. Studies (Heyl & Currie 1985; Harebottle & Delport 2000) have shown that opening the mouth too frequently, and at the wrong time, can have significant impacts on waterbird richness and abundance and may have detrimental effects on the reproductive success of those waterbirds breeding at the estuary. | ||
| CWAC history | The estuary was first counted in July 1993. Counts have since been conducted on a regular, six monthly basis by five teams of observers made up from members of the Tygerberg, Hermanus, Kleinmond, Somerset West and Cape Bird Clubs. | ||
| Waterbird highlights |
CWAC data shows that the estuary can support up to 60 different waterbird species and 10 000 individuals at any one time, although summer counts are generally higher due to the influx of migrants. Redknobbed Coot Fulica cristata is by far the dominant species - up to 8000 birds have been counted – comprising up to 75% of all waterbirds at the site. Other abundant species that can be seen regularly include Reed Cormorant Phalacrocorax africanus, Greater Flamingo Phoenicopterus ruber, Egyptian Goose Alopochen aegyptiacus, Yellowbilled Duck Anas undulata, Cape Shoveller Anas smithii, Kittlitz's Plover Charadrius pecuarius, Blackwinged Stilt Himantopus himantopus, Kelp Gull Larus dominicanus, Hartlaub's Gull Larus hartlaubii, Caspian Tern Sterna caspia and Swift Tern Sterna bergii. Migrant waders are dominated in summer by Ringed Plover Charadrius hiaticula, Common Sandpiper Tringa hypoleucos, Curlew Sandpiper Calidris ferruginea and Little Stint Calidris minuta with large flocks of Common Tern Sterna hirundo regularly recorded roosting near the mouth. The estuary holds globally significant numbers of Great Crested Grebe Podiceps cristatus (152), Blacknecked Grebe Podiceps nigricollis (1 100), Yellowbilled Duck, (811), Cape Shoveller (404), Hartlaub's Gull (285) and Redknobbed Coot (7518). | ||
| Count data |
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| Breeding records | Confirmed
Suspected | ||
| Threatened waterbirds Barnes 2000 |
The following Red Data species have been recorded at the estuary:
Vulnerable: Near-threatened: |
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| Other birding highlights | |
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| Conservation issues | |||
| Photo gallery | The following sets of photos were taken using the fixed-point technique and demonstrates how the condition of the wetland, and habitat change, can help draw conclusions about waterbird abundance at a site. Note how much fuller the estuary was in January 2000 compared with January 1996!
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View looking westwards from the yacht club
