Effect of climatic change on the duration of the breeding season in three European thrushes

Capsule Evidence for extension of breeding seasons in Song Thrushes and Blackbirds (multiple-brooded species) and shortening in Fieldfares (a single-brooded species). Aims To analyse breeding data from central Europe during 1964-2006 in relation to climatic conditions operating at breeding and wintering grounds, and to compare breeding phenology in urban and rural habitats. Methods Using chick ringing data we evaluated long-term changes in breeding phenology of Fieldfares Turdus pilaris, Song Thrushes T. philomelos and Common Blackbirds T. merula. Changes in phenology were analysed for the 5th percentile, median, 95th percentile, inter-quantile range (IQR) and brood size. Results All thrushes showed consistent trends towards earlier onset of breeding. However, there was a contrasting pattern in the later phenological characteristics (median, 95th percentile and IQR) that were associated with single- versus multiple-brooded species. The single-brooded Fieldfares revealed an advancing trend in all phenological phases, which caused shortening of its breeding period. In contrast, the multiple-brooded Song Thrushes and Blackbirds delayed both medians and the 95th percentiles of breeding dates leading to extension of their breeding seasons. Temperatures at both wintering and breeding grounds were generally negatively associated with the onset of breeding. Urban birds bred significantly earlier than their rural conspecifics, but brood sizes did not differ. Conclusion Multiple-brooded species may respond differently to increasing spring temperatures than single-brooded species.