The study also found that when the animals’ bodies shrank.
Their wings did not, meaning birds now tend to be “wingier” in proportion to their bodies. That could be due to a regulation of body temperature.
Migratory birds in North America are getting smaller, a change researchers attribute to the rapidly warming climate , a UCLA study reveals.
The research, published in Nature Ecology and Evolution , found that over the last three decades, the body mass of 105 bird species in the analysis decreased by an average of 0.6%, but by as much as 3.0% in some species. . Tree swallows, for example, were down 2.8%, robins were down 1.2%, and woodpeckers were down 2.2%.
Those figures may not sound alarming at first. But in evolutionary terms, they are dramatic changes in a very short time.
The article reveals the extent to which temperature affects the physical characteristics of animals, said Casey Youngflesh, an ecologist at UCLA and lead author of the study.
“This is large-scale evidence that climate change is literally shaping the way species look,” Youngflesh said.
Morgan Tingley, an ecologist at UCLA and lead author of the study, said the fact that the phenomenon occurred for the vast majority of species in the research, not just one or a few, is clear evidence that climate change is guilty.
“There is no other plausible hypothesis for why we would observe these changes over time,” he said. “If we had only measured changes in body size in one species, it would be easy to imagine that something strange was happening in that species, due to its natural history or range, for example. But since we found this signal consistently throughout So many many species, in such a large swath of North America covering so many different environments, there is no plausible hypothesis left except climate change .”
Small bodies help animals cope with higher temperatures because the higher surface area to volume ratio helps dissipate heat. On the contrary, the larger and rounder bodies, typical of birds from colder regions, conserve heat better.
The study found that bird size varies predictably by location; birds in warmer places tend to have smaller bodies than those in colder places. He also found that birds in warmer places also got smaller and at a faster rate, evidence that animals are adapting, regardless of their location, to warmer temperatures.
However, the researchers also found that the changes didn’t keep pace with warming: Their reduction in body size was only about 40% of what scientists would have expected based on the increase in temperature over the course of the study. That means animals are at higher risk for heat-related health problems and death.
The wings do not shrink
But the study found that even when the animals’ bodies shrank, their wings didn’t, meaning birds now tend to be “wingier” in proportion to their bodies. That could be in part because the wings aren’t helpful in regulating body temperature, Tingley said.
“The wings are mostly feathers, so birds don’t use them to dissipate heat,” he said. “They mainly use their legs, beak and mouth to regulate body temperature.”
The researchers also discovered another factor important to the size and shape of birds . The study presents the first large-scale evidence that birds living at higher elevations tend to have longer wings, an adaptation that helps birds fly in the thin air of mountainous environments. In these places, the birds have longer wings and smaller bodies despite the cooler temperatures.
The research was conducted using data from the Monitoring Avian Productivity and Survivorship (MAPS) program, which is run by Bird Populations, a nonprofit organization that studies why bird populations are declining. Since 1989, MAPS has collected bird measurements and other data from more than 1,200 bird -banding stations in North America.
Thanks to that trove of information, the UCLA study is unprecedented in its magnitude, in terms of the number of species it tracked and the time it covered.
Scientists have been investigating the ways that animals respond to climate change , trying to discover what their limits are. Tingley said previous research has shown that migratory birds have the advantage of being able to fly to colder climates to escape high temperatures, but the UCLA-led study demonstrates another way they adapt.
“We’re constantly amazed at how species are changing in ways we didn’t think they would,” Tingley said. “While this change doesn’t completely offset all of the warming they’re going to experience, it appears to be a critical and underappreciated tool in their toolbox.”
(With information from Europe Press)