Researchers analysed 60 years of GBIF-mediated occurrences across 285 land-bird species in the contiguous United States (excluding Alaska and Hawaii). More than five million records were cross-referenced with data on weather conditions from the same period, creating models predicting how changes in climate affect breeding-bird distributions. The results showed that these distributions are shifting at an average speed of 1.27 km/year, double the global estimates. Surprisingly, the direction of these shifts is not just northward, but also westward in 27.4% of species. While average temperature is the most important factor in long-term changes, short-term precipitation and extreme conditions also influence many species. Predicted increases in species richness in the Midwest and East hinge on whether these areas can sustain the affected species in the future in lands continuously developed by humans.
Bateman, B. L., Pidgeon, A. M., Radeloff, V. C., VanDerWal, J., Thogmartin, W. E., Vavrus, S. J., & Heglund, P. J. (2015). The pace of past climate change vs. potential bird distributions and land use in the United States. Global Change Biology. doi:10.1111/gcb.13154