The effect of weather on lesser kestrel breeding success: can climate change explain historical population declines?

Abstract

Summary We model the effect of annual weather conditions on lesser kestrel Falco naumanni breeding success in South‐western Spain. Models indicate that rainfall is a good predictor of breeding success and has in general a positive effect on reproduction. Rainfall and temperature in spring, during the courtship period, influence colony occupancy rate. Mean minimum temperatures have a positive effect on nest occupation while the relationship between occupation and rainfall is curvilinear with an optimum around 84 mm. Nest success rate is influenced positively by rainfall in winter and negatively by rainfall during the nestling period. The mean number of chicks per successful nest is positively influenced by rainfall during the winter, arrival, courtship, and incubation periods. Rainfall during these periods explains 35% of the variance in this breeding parameter. Nestling body condition is affected positively by rainfall during the courtship and incubation periods. Models that consider the amount of rainfall at each colony in periods defined by the breeding phenology of the lesser kestrel outperform those based on total annual rainfall or on winter NAO‐index. Although rainfall in spring has declined significantly since 1966, retrospective predictions of lesser kestrel population growth rate at our colonies indicate that the effect of climate change on breeding success cannot be held responsible for the historical population decline.