Cape Gannet Morus capensis year-round presence off the southern Cape coast of South Africa

Abstract

The year-round presence and abundance of Cape Gannets Morus capensis in the greater Wilderness waters (Western Cape, South Africa) were monitored through a land-based observational study, 330 km (straight-line distance) from the nearest breeding colony, Bird Island Algoa Bay. Between 2022 and 2025, gannets were observed in 65% (n = 110) of breeding-season surveys and in 94% (n = 124) of non-breeding season surveys. The number of gannets per survey was significantly lower (U = 4373, p = < 0.001) during the breeding season compared to the non-breeding season. Per age class, the maximum number of gannets recorded in a survey was 325 adults and 74 juveniles in the breeding season, and 1 082 adults and 124 juveniles in the non-breeding season. During both seasons gannets were observed diving, resting and flying. This study supplements the (limited) available information on the distribution and abundance of the endangered Cape Gannets along the southern Cape coast, especially in the non-breeding season, necessary to aid conservation planning.