Ardea
Official journal of the Netherlands Ornithologists' Union

login


[close window] [previous abstract] [next abstract]

Kalejta B. (1992) Time budgets and predatory impact of waders at the Berg River Estuary, South Africa. ARDEA 80 (3): 327-342
The energy intake rates and activity budgets of selected wader species foraging on the intertidal mudflats of the Berg River estuary, South Africa, were studied from December 1987 to April 1989. For the majority of waders, daytime foraging alone was not sufficient to meet their daily energy requirements. Birds redress these deficits by foraging on the mudflats at night and/or by foraging in saltmarshes and saltpans during high tide. Increased energy demands during the pre-migration period are met by increased foraging activities both at night and during the day. Visual foragers spent a higher proportion of the available time foraging at night than during the day, whereas the reverse was true for predominantly tactilely-foraging species. Pecking rate, distance travelled to capture prey and frequency of searching by Grey Plovers were reduced at night. The total annual prey consumption by waders at the Berg River estuary was 267 91 (SE) kg ha-1y-1. If migrant waders foraged on intertidal mudflats alone they would have removed 26.2 10.4% of the total annual production of invertebrates. The highest predation pressure by shorebirds coincided with the period of highest production of the most important invertebrate prey. The rate of prey removal by shorebirds at the Berg River estuary is one of the highest recorded on the east Atlantic seaboard, and was sustained by high invertebrate productivity.


[close window] [previous abstract] [next abstract]