We analysed the effects of local-(sea-surface temperature [SST] and windspeed) and large-(multivariate El Niño index) scale weather conditions and timing of breeding on reproductive parameters of tropical roseate terns Sterna dougallii on Aride Island, Seychelles, using up to 17 years of data. The size of the breeding population and initiation of breeding were negatively and positively correlated, respectively, with both SST and the multivariate El Niño index for the laying season (MayJune). It is the first time that an El Niño index obtained for the Pacific Ocean is shown to be correlated with reproductive parameters of seabirds in the Indian Ocean. Hatching success decreased significantly with later initiation of breeding. Virtually no chicks fledged when breeding started in June (40% of the years monitored). We suggest that oceanographic conditions over a relatively large scale have an influence on tern arrival date to the breeding grounds and that SST around the breeding colony influences the number of birds that attempt to breed. Despite the influence of factors such as predatory fish on food availability, this influence appears to be overridden by the importance of weather events and oceanographic conditions, which are likely to determine marine productivity. This study suggests that ecosystem-level phenomena appear to be important in shaping the population dynamics of tropical roseate terns.

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SummaryThe Seychelles Warbler was once a highly threatened single-island endemic species with a population of 26 individuals confined to Cousin Island in the inner Seychelles. Following long-term management of Cousin, the population steadily recovered to around 300- 360 birds. Given the vulnerability of one small island in the Indian Ocean, the possibility of establishing the species on additional islands had been proposed as a priority conservation measure. This paper describes the successful translocation of 29 Seychelles Warblers from Cousin to Aride, summarizes the ecological studies carried out prior to, during and after the translocation and documents the subsequent establishment of the new population. It is considered that the Seychelles Warbler will soon no longer be a globally threatened species.

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