A new study by researchers at Yale University looks at the way bird morphology is changing in response to the warming climate. As temperatures rise, birds’ bodies are growing smaller, but their wings are growing longer.
In the study, published in the Proceedings of the National Academy of Sciences, the scientists analyzed two independently collected datasets containing 40 years of morphology changes in 129 bird species comprising 52 migratory species in North America and 77 South American species.
In both datasets, similar changes were observed over the 40-year period. The overall trend makes sense given that being smaller and having longer wings both would help birds to stay cool in warmer weather. What was less obvious was that the changes to the birds were much greater among the smallest bird species.
One possible explanation is that smaller species tend to reproduce on a shorter time scale and therefore evolve more quickly. However, the study found no link between generation length and the changes in body size.
Another possible explanation is that smaller species tend to have larger populations, which means there is a greater chance of having individuals with desirable new traits that can get passed on. But the scientists found no link between population size and shifts in body size either.
At this point, it is unclear why smaller birds are shrinking more. More research is needed to figure out why larger birds are slower to adapt to climate change. In general, larger species of animals have an increased risk of extinction. This new research suggests that larger body size exacerbates extinction risk by limiting the ability for birds to adapt to the changes we are making to the climate.
Birds Are Shrinking as the Climate Warms — and Small Birds Are Shrinking Faster
Photo, posted October 30, 2018, courtesy of N. Lewis / National Park Service via Flickr.
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