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Seabirds, because they feed near to the top of food webs, are indicator species for the health of marine ecosystems. The populations of several seabird species in the Benguela upwelling ecosystem have undergone large decreases in the last 50 to 100 years, linked in many cases to losses of their prey base either through large-scale changes in the ecosystem or the impacts of man.
The bank cormorant Phalacrocorax neglectus is a poorly studied seabird that breeds only in South Africa and Namibia. The population decreased by 66% over the last 40 years to around 3 000 pairs. The species is considered Endangered by the IUCN Red List, meaning it is has a very high risk of extinction in the wild.
Our research focusses on conservation research for this species. The mechanisms driving the population trends have not been fully explored or understood. Human disturbance, displacement by seals, and changes in prey availability have been implicated in the past, while a more recent study suggested a role for climate variability that had previously been unexplored. Little routine monitoring or directed research has been carried out on bank cormorants in South Africa since the 1970's. Starting in 2012, we initiated a three-year study to (1) examine the role that changes in prey availability has played in the past declines in southern Africa and (2) explore the hypothesis that broad-scale changes in climate and the southern Benguela Upwelling System could have contributed to the past declines.
The project used monitoring primarily based on visual observation and analysis of video data. Breeding success, chick-provisioning behaviour and thermoregulatory behaviour were assessed at three colonies in the Western Cape (Robben Island, Jutten Island, Stony Point).
Future work could extend the monitoring to include the deployment of remote-sensing technology (GPS loggers) to study foraging behaviour and the ringing of chicks to allow for survival analysis. Through collaborations with colleagues in Namibia data will be gathered and analysed for the same four variables at Mercury Island, Namibia. This is a site for which some baseline data on bank cormorants exists.
Although the initial project has now concluded, I am working with a number of partners in the hope of developing an annual monitoring programme, for these birds. Using a combination of methods above, this would improve our understanding of the factors driving the population dynamics of the species in South Africa. In doing so, we will have initiated long-term datasets to contribute to conservation decision making and ecosystem modelling studies. The ultimate goal is to propose a collaborative management plan for the conservation of this endangered species.
This project was a collaboration between the Animal Demography Unit, the Percy FitzPatrick Institute of African Ornithology and the Department of Forestry, Fisheries and the Environment. The work was funded by a SEAChange grant from the National Research Foundation. Two research students who worked on the project graduated in 2014 and some of the results from the project were summarised in publications in Conservation Biology and Conservation Physiology.
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