Temporal variation in breeding,foraging and bird sanctuary visitation by a Southern African Population of great white pelicans Pelecanus onocratalus

Temporal variation in visitation, breeding and foraging during 1977–1978 at a breeding site and a proclaimed bird sanctuary are described for a southern African population of great white pelicans Pelecanus onocratalus. Foraging activity and sanctuary visitation were at low levels during the austral winter (May–August). The pelicans bred at only one site, Dassen Island (33° 25t?, 18° 12′ E), in three major waves in spring and summer (September–March), coinciding with periods of high visitation and foraging activity at Rondevlei Bird Sanctuary (34° 04′S, 18° 30′ E), an important foraging and roosting site within the range of the population. Temporal variation in these aspects of pelican biology is influenced by the fluctuating availability of suitable foraging habitat and fish prey. Water depth and rainfall, those environmental factors which appear to affect the availability of foraging habitat and fish prey, were correlated strongly negatively with measures of pelican foraging activity and sanctuary visitation during 1977–1978. They were also negatively correlated with measures of sanctuary visitation calculated for a 22-year period. Therefore, these factors may have influenced patterns of foraging and visitation of this great white pelican population over the long term.