Abstract: Breeding attempts by the African penguin Spheniscus demersus at a colony on Marcus Island, Saldanha Bay, South Africa, decreased by 14% per year during 1979-1985. Annual adult survival was 33.3-70.4%. Nesting success at Marcus Island was similar to that at other African penguin colonies of St Croix and Dassen islands and at colonies in other areas of other penguin species not undergoing population decreases. Minimum survival of juveniles in the first year of life was only 4% of the level needed to sustain a stable population.