Ardea
Official journal of the Netherlands Ornithologists' Union

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Ryan P.G., Edwards L. & Pichegru L. (2012) African Penguins Spheniscus demersus, bait balls and the Allee effect. ARDEA 100 (1): 89-94
We report co-operative group foraging in the African Penguin Spheniscus demersus. Groups of approximately 25165 African Penguins were observed circling schools of pelagic fish, sometimes forcing them to the surface. During this behaviour 6675% of penguins were underwater at any given time. Smaller numbers of African Penguins also joined foraging groups of Cape Gannets Morus capensis and Cape Cormorants Phalacrocorax capensis, but did not appear to corral fish schools when outnumbered by these species. African Penguins are listed as Endangered due to ongoing rapid population decreases. If group foraging confers an advantage to African Penguins, their dwindling populations may suffer from an Allee effect as colonies become too small to support sufficient densities of birds for foraging groups to form.


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