Waterbirds at the Klein River Estuary: 2001–2009 

Summary of the 'Report on the status of waterbirds at the Klein River Estuary : 2001-2009', by Doug Harebottle, Animal Demography Unit, Department of Zoology, UCT

Monitoring of waterbirds has been carried out at the estuary since February 2001 as part of the Coordinated Waterbird Counts (CWAC) programme. CWAC is a national, volunteer–based programme which collates waterbird count data from a range of wetland sites across South Africa and is coordinated by the Animal Demography Unit at the University of Cape Town. 

Analyses of waterbird data considered overall waterbird richness and seasonal abundance at the estuary from February 2001–July 2009. Species were grouped into occurrence status (African resident or Palearctic migrant), family group (ducks, grebes, coot, cormorants, shorebirds, waders, gulls and terns) and feeding guild (herbivore, invertebrate feeder or piscivore). Shorebirds here refer to those species generally known as ‘waders’ while waders refer to large wading species such as herons, egrets, flamingos, spoonbills and ibises. 

Overall 34 waterbird surveys were conducted at the estuary from February 2001–July 2009. 

A total of 65 waterbird species was recorded at the estuary, and included 49 resident species and 16 Palearctic migrants. Of the resident species, six comprised Red Data species while five are southern African endemics. One species, Goliath Heron, is a Western Cape rarity, while two species, White-backed Duck and African Black Duck are uncommon species in the Western Cape. 

The mean number of species counted per survey was 30 in summer and 24 in winter. In terms of overall abundance, mean counts of 2419 ± 1809.8 and 2016 ± 1220 waterbirds occurred at the estuary during summer and winter respectively. Waterfowl dominated both seasons, and comprised 68.3% of all waterbirds during summer and 84.9% during winter. During summer, migrant (Palearctic) terns comprised 11.3% and resident gulls 6.3%. In winter, and in the absence of the Palearctic migrants, the other abundant groups were the resident shorerbirds and gulls, each comprising 3.7% to the overall seasonal abundance. 

In terms of species, Red-knobbed Coot dominated overall waterbird abundance and comprised 59% and 77% of the total summer and winter waterbird populations. Common Tern, Yellow-billed Duck, Hartlaub’s Gull and Cape Shoveler comprised most of the other abundant species in summer. In winter, Yellow-billed Duck, Cape Shoveler and Hartlaub’s Gull made up most of the other dominant species. 

The month with the average highest count is December (5748 birds) and the lowest average count is August (324 birds), although results are based on variable count frequencies. Considering maximum counts for all species, the lake can support up to 12 261 waterbirds. 

From a population and conservation status perspective, the estuary is important for ten species - six Red Data species and four species reaching important threshold levels. The site does qualify as a RAMSAR site (or wetland of international importance) based on the numbers of two species, African Black Oystercatcher and Caspian Tern although the frequency at which these species meet the RAMSAR criteria are relatively low. Based on the numbers of African Black Oystercatcher, Caspian Tern, White-breasted Cormorant and Hartlaub’s Gull, the site also qualifies as a sub-regional Important Bird Area. These species occur more regularly at this level and therefore give stronger weight to this designation than the RAMSAR status.  

Statistics: