TIZO 'La Niña'-driven Atlantic storms affect winter survival of Mediterranean Cory's Shearwaters

Abstract

To test a previous hypothesis of a relationship between the adult survival rates of Mediterranean Cory's Shearwaters (Calonectris d. diomedea) and La Niña-driven Atlantic storms, we analysed 18 years of capture-mark-recapture data of adults ringed at a breeding colony in the Tremiti Islands. We used the program MARK to model survival and capture probabilities as functions of time-specific external variables such as the effect of temporal variations on capture probability and of climatic (ENSO, NAO, SST) and non-climatic factors (oil spills and fishery production) on shearwater survival. The model selection process of the program indicated that survival declined the most in La Niña years, when a greater number of storms were expected in the wintering range; oil spills and interaction with fisheries are worthy of attention too. Our analysis confirms the results of previous work, suggesting that the El Niño Southern Oscillation (ENSO) cycle is the main force governing climatic and ecological factors responsible for lowering Cory's Shearwater survival rates during La Niña years, probably through the effects of the enhanced Atlantic hurricane season. © 2010 Unione Zoologica Italiana.