Fluctuations in bird numbers on sewage treatment ponds in an arid environment, South Africa

Abstract

Regular twice-monthly counts of birds associated with water at the Prince Albert sewage disposal facility recorded 69 species, of which 16 species (23.5%) were waterbirds (ducks, Red-knobbed Coot Fulica cristata and Little Grebe Tachybaptus ruficollis) and 21 species were shorebirds (30.9%). The remainder of the species were birds of reed beds (11; 16.2%), weedy or shrubby habitats around the edges of the ponds (12; 17.6%) or that hawked prey over the ponds (9; 13.2%). The numbers of shorebirds and waterbirds were positively and significantly correlated and were highly variable over time. There were no movements to the sewage facility by waterfowl specifically to moult. The presence of both waterbirds and shorebirds showed an historic movement pattern, with peak numbers correlated with long-term average peak rainfall months.