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African Penguin Dispersal

A juvenile African Penguin at sea equipped with a Platform Terminal Transmitter.
Image © Cheryl-Samantha Owen/www.samowenphotography.com





A silicone-rubber flipper band fitted to an African Penguin. These bands are individually numbered and are used to infer information on survival and movements of the species. 
Image © Kate Robinson, ADU.

One of the possible causes for the recent decline of the African penguin Spheniscus demersus population in South Africa is a mismatch between the breeding localities in the Western Cape and the availability of their main prey, sardine and anchovy. Penguins must swim to find their food and breeding birds must deliver food to the nest to ensure chick survival. As a result, they have little flexibility to shift their foraging ranges beyond about 20–30 km when breeding for African penguins.

Juvenile birds, on the other hand, are theoretically free to disperse to areas where resources are more plentiful and may move considerable distances from the colony at which they hatched. Although African penguins are faithful to their colonies once they start breeding, in the last three decades they have initiated three new mainland breeding colonies and re-colonised one former breeding site. Most of the birds that bred at these new colonies in their early years were first time breeders that moved from other colonies. This emigration is thought to be a response to changes in the local or regional availability of prey, but seabird breeding colonies are restricted to sites free from disturbance and protected from land-based predators.

Based on this knowledge, as well as the success of interventions to hand-rear chicks orphaned following oil spills, it has been proposed to initiate and protect a new mainland breeding colony closer to the breeding stocks of the sardine and anchovy. The African penguin Chick Bolstering Project (CBP) was initiated to investigate whether chicks abandoned by their parents and reared to fledging age by SANCCOB could be used to bolster declining colonies and establish a new colony on the south coast. For such an endeavour to be successful, it is crucial that we understand whether these chicks survive and recruit into breeding populations as well as wild chicks. Some insight into the mechanisms that govern whether fledglings return to the colony in which they hatched or disperse to other sites is also crucial. Unfortunately, the period of the African penguin life cycle from fledging until they return to breed at around three to four years old is poorly studied.

We have used a combination of data from chicks marked with flipper bands (more recently micro-chips) and data obtained from tracking juveniles at sea (see images, left) to help understand at what age penguins develop the knowledge of where they will breed and how this decision may relate to the conditions they experience in the nest as well as at sea post fledging. To date, we have identify some key foraging areas used by juvenile penguins on the west coasts of South Africa and Namibia and contributed to population modelling. More information on the tracking component of this study can be found here. Updates on this project have been posted on Penguin Watch and in Environment magazine (see Publications).

The Chick Bolstering Project is a collaboration between SANCCOB, the Bristol Conservation and Science Foundation, the Animal Demography Unit, the Department of Environmental Affairs (Oceans and Coasts), CapeNature, Robben Island Museum and the International Fund for Animal Welfare (IFAW).