Foraging behaviour of bank cormorants in Namibia: implications for conservation

Abstract

We studied the foraging and diving behaviour of male bank cormorants Phalacrocorax neglectus at Mercury Island, Namibia, during the 2007-2008 breeding season. The island hosts the world's largest breeding colony of this endangered species. Population numbers are currently stable at Mercury Island, whereas numbers at other colonies in Namibia are decreasing, including those at formerly important colonies. This trend is presumably due to reduced food availability. At Mercury Island, bank cormorants foraged inshore (ca. 2 km off the coast) in close vicinity to their breeding site (ca. 3 km off the colony) and dived to an average depth of 30 m. Diet at Mercury Island was domi- nated by demersally occurring pelagic goby Sufflogobius bibarbatus. Our findings suggest that bank cormorants are benthic feeders along their entire range and that their foraging behaviour in Namibia does not differ from that suspected in South Africa. Further studies, extending to other breeding sites, are needed to explain the different population trends and how these may be influenced by food avail- ability. The identification of important foraging sites will play a crucial role in the management of Namibia's first Marine Protected Area and will contribute towards the protection of this species.