Differential responses of boobies and other seabirds in the Galapagos to the 1986-87 El Nino-Southern Oscillation event

Abstract

The impact of the 1986-87 El Nido-Southern Oscillation (ENSO) event on seabirds in the Galapagos Islands was generally less severe than that of the previous ENSO in 1982-83. Sea surface temperatures (SST) rose to levels comparable to those of 4 ENSOs pnor to the 1982-83 event. SST became anomalous approximately in January and had returned to typical levels by July. Blue-footed booby Sula nebouxii reproductive attempts failed throughout the archipelago, and breeding colonies were deserted, shortly after SST became unusually warm in January. Masked boobies S. dactylatra, redfooted boobies S. sula and several other species were apparently unaffected by the anomalous conditions, or temporarily suspended breeding for several months. A gradient in both SST and in the ENSO's impact on some seabirds was evident, with populations nesting in the cooler south of the archipelago affected less than those in the warmer north. At one colony studied both before and during the ENSO, blue-footed booby failure was associated with apparent reductions in both availablllty and body size of their primary prey item.