Attribution index for changes in migratory bird distributions: The role of climate change over the past 50Â years in China

To examine whether changes in the distribution of migratory birds can be attributed to climate change, we analyzed the changes in the distributions of the species relative to climate change over the past 50 years in China. Long-term distribution records of 14 species or subspecies of migratory birds were used together with grey relationship analysis, fuzzy sets classification techniques, the consistency index and the attribution index. Over the past 50 years, edges of distributions expanded. Different species expanded to different directions driven directly by the climate change or driven secondary by the climate change or other habitat changes, and for the majority of birds, these changes were mainly related to the thermal index. Driven by climatic factors over the past years, the northern limits of more than one-half of the birds shifted northward with fluctuations. In addition, the consistency indices of observed vs. predicted changes in the distribution boundaries or the distribution centers were higher for particular migratory birds. The changes in the center latitude or longitude of the distribution of 4 species or subspecies, the northern boundary of 6 species or subspecies, the southern boundary of 1 subspecies, the eastern boundary of 5 species or subspecies and the western boundary of 3 species or subspecies can be attributed to climate change.