The influence of global warming on timing of migration and breeding of passerine bird in the twentieth century

The long-tenn (1959-2002) monitoring data on the timing of migration and breeding of 25 short- and long-distance migrants showed that during two recent decades, the earlier arrival and breeding were recorded more frequently. The timing of autumn migration did not reveal a significant trend of changes in the majority of species over the study period. In 16 species, a significant negative relationship of the timing of arrival and breeding with the mean spring monthly temperatures and index NAO (North Atlantic Oscillation) was revealed in the February-March period. The earlier spring migration and breeding of birds in short- and long-distance migrants were related to higher spring temperatures and index NAO. In many species, a positive relationship was found between the date of autumn migration and the timing of breeding in the Courish population. The analysis of relationships between the timing of autumn migration and the ambient autumn temperatures and index NAO in August-October did not reveal a significant correlation in the majority of the species. On the basis of these data, the conclusion was made that the significant shifts in the timing of spring migration and breeding towards earlier dates in many short- and long-distance migrants were caused primarily by climate fluctuations in the Northern Hemisphere. The hypothesis is suggested that during the recent two decades, not only arrival dates, but also the onset of spring migration in wintering of passerines within Europe and Africa was shifted under the influence of environmental factors related to the global climate change. The forecast of future trends in the arrival and breeding of birds in Europe and other regions depends primarily on the dynamics of winter and spring temperatures in the Northern Hemisphere. The spring migration and breeding of birds will occur earlier if climate in the Northern Hemisphere is getting warmer. Future changes in the timing of autumn migration will depend on the dynamics of arrival and breeding timing.