In a new study, UCLA ecologists Casey Youngflesh and Morgan Tingley suggest global warming is reducing the body mass of migratory birds and affecting the proportion of their wingspan. The 30-year study tracked changes in 105 migratory bird species across North America, and found that birds’ body mass declined by an average of 0.6% over the past three decades.

Tingley, the study’s senior author, said the fact that the phenomenon occurred across most species in the research is clear evidence that climate change is the culprit. “There is no other plausible hypothesis for why we would observe these changes over time,” he added. “If we had only measured body size changes in one species, it would be easy to imagine that something odd was going on in that species, due to its natural history or range, for example. But given that we find this signal consistently across so many species, across such a huge swath of North America covering lots of different environments, there is no remaining plausible hypothesis except for climate change.”

Tingley said previous research has shown that migratory birds have the advantage of being able to fly to cooler climates to escape high temperatures, but the UCLA-led study demonstrates another way they adjust.

Read more about the study on bird adaptations in response to climate change at UCLA Newsroom.

Study Authors:

James Saracco, The Institute for Bird Populations, Petaluma, CA

Rodney Siegel, The Institute for Bird Populations, Petaluma, CA

Morgan Tingley, UCLA Department of Ecology and Evolutionary Biology

Casey Youngflesh, UCLA Department of Ecology and Evolutionary Biology
 

Image Source: Santa Monica Mountains National Recreation Area