Use of a small, intermittently-open estuary by waterbirds: a case study of the East Kleinemonde Estuary, Eastern Cape, South Africa

Abstract

Little is known of the use and importance of South African small, intermittently-open estuaries to waterbirds. Waterbird activities were monitored in a section of the East Kleinemonde Estuary on the south-east coast of South Africa from June 2004 to May 2005. Counts along the whole estuary were conducted approximately weekly from March 2005 to November 2006, and numbers were related to daily water level measurements. The estuary was used mainly for roosting and maintenance (81% of all records), the majority of which was by wading piscivores (50%). Herbivores were largely absent in summer, when submerged macrophyte cover was zero. There was a significant difference in activity patterns between summer and winter for all feeding guilds except aerial diving piscivores. Most birds probably overnighted elsewhere. Pursuit-swimming piscivore numbers increased and wading and aerial-diving piscivores decreased with rising water levels. This study showed that intermittently-open estuaries are primarily utilised by resident piscivorous birds and are an important habitat, not only for feeding, but also for resting purposes. Changes in water level affected feeding guilds differently by changing habitat availability.

Keywords: activity patterns, community composition, estuarine birds, mouth dynamics, temporarily open/closed estuary

African Journal of Aquatic Science 2012, 37(2): 183–190