Birds in the Americas are shrinking and developing longer wings as the Earth warms; the smaller the bird species, the faster the change. According to Co-senior author Brian Weeks, an Evolutionary Ecologist at the University of Michigan School for Environment and Sustainability, the researchers discovered that smaller birds appeared to evolve faster because they experience stronger selection or are more responsive to it. However, why smaller-bodied species are changing more quickly remains an open question. The results suggest that a large body size could exacerbate extinction risk by limiting the potential to adapt to ongoing climate change.
