Increasing breeding success of an Endangered penguin: artificial nests or culling predatory gulls?

Abstract

SummaryDrastic recent decreases in numbers of the ‘Endangered’ African Penguin Spheniscus demersus highlight the need for conservation efforts to reverse this trend. Habitat reduction due to former guano scraping forces penguins to breed in surface nests, which are vulnerable to predation by Kelp Gulls Larus dominicanus and to extreme weather events. Here I compare gull predation and the success of penguins breeding in surface nests and two types of artificial nests, before (2009) and after (2010–2011), the removal of predatory gulls from Bird Island, South Africa. Both culling gulls and providing artificial nests improved penguin chick survival, but post-culling chick survival was lower in surface nests than in artificial nests, suggesting a major impact of weather on chick mortality. Success of artificial nests was design-dependent, with poor hatching success in fibreglass burrows (probably due to high ambient temperatures), but nests under 50 cm cement pipes cut in half had the highest breeding success. Therefore, appropriately designed artificial nests can enhance African Penguin breeding success, shielding them from both predation and extreme weather events. Where implementing such nests is constrained, controlling Kelp Gulls can also enhance penguin production, especially during years of low food availability when the vulnerability of chicks to predation is exacerbated. Such a strategy would, however, require ongoing management, as territories freed by culled gulls are constantly filled with new individuals. The alarming trend in African Penguin numbers justifies robust conservation strategies, although these should also be concomitant with limiting oil spills and increasing food availability around their colonies.