Patterns of covariation among weather conditions, winter North Atlantic Oscillation index and reproductive traits in Mediterranean kestrels


  • Editor: Virginia Hayssen

David Costantini, Division of Ecology and Evolutionary Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Graham Kerr Building, Glasgow G12 8QQ, UK.


Changes in local weather conditions may affect reproduction in birds. In this study, we evaluated how changes in both local weather and winter North Atlantic Oscillation (the NAO, an index of non-local climatic conditions) could explain variation in selected reproductive traits (laying date, clutch size, hatching and fledging success) in Mediterranean kestrels Falco tinnunculus over 10 years. Kestrels (1) delayed the laying date in rainier springs; (2) laid smaller clutches after warmer and rainier winters, independently from the laying date; (3) had higher hatching success after warmer and dry winters and in warmer and rainier springs; (4) had higher fledging success in warmer and rainier springs. Thus, changes in the weather and the winter NAO index affected reproductive decisions and reproductive success. Predicting the long-term effects of global warming on the viability of Mediterranean populations of kestrels and other birds of prey is difficult. Whether the reproduction of birds of prey will be positively or negatively affected by global warming will depend on the relative importance of changes in temperature and rainfall.