Original Articles

Waterbirds at Paarl Waste Water Treatment Works, South Africa, 1994–2004: seasonality, trends and conservation importance

Published in: Ostrich: Journal of African Ornithology
Volume 79, issue 2, 2008, pages: 147–163
DOI: 10.2989/OSTRICH.2008.


Numbers of waterbirds were counted monthly from May 1994 to April 2004 at Paarl Waste Water Treatment Works, South Africa. Seventy-two waterbird species were recorded, of which 33 species (46%) were recorded breeding. Mean summer and winter counts were 2822 ± 504 and 1651 ± 251 birds, respectively. Summer peaks were driven primarily by large numbers of White-winged Terns (mean summer count = 858 or 34% of total count). Resident species dominated from December to April, whereas Palaearctic migrants peaked from December to March. Ducks and geese had greatest numbers from December to April and resident waders and grebes peaked from April to July. Flamingos peaked in October and November with another small peak in June. Gulls and terns had two peaks, one in November–March, driven by migrant White-winged Terns, the other in July and August, driven by abundance of resident Benguelan (Hartlaub's) Gulls. White-winged Terns showed the greatest decline (82%) of all species. Influx of Little Grebe and Red-billed Teal during winter showed a positive correlation with rainfall, while Egyptian Goose, Yellow-billed Duck and Cape Shoveler numbers declined as winter and spring rainfall increased. Paarl Waste Water Treatment Works ranked as the second-most important wastewater treatment works for waterbirds in the Cape Town metropole. It supported globally and regionally important numbers of 11 species and qualifies as a global and/or subregional Important Bird Area and Ramsar Site.

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