Climate change is causing significant changes in ecosystems worldwide, including alterations to the physiology and behavior of many animal species. One group of animals particularly vulnerable to these changes are birds, known for their sensitivity to shifts in temperature and precipitation patterns. As such, understanding how different bird species respond to climate change is a critical research area for conservation biologists.
Recent research led by the University of Michigan suggests that bird species’ body size predicts the rate of change in a warming world. The study found that smaller birds tend to adapt faster than larger ones when it comes to responding to climate change.
In the study, researchers analyzed data on 129 bird species from around the world, measuring changes in bill length, wing length, and tarsus length over 40 years. The researchers obtained these measurements from museum specimens and databases and used statistical methods to examine the relationship between bird body size and the rate of morphological change. They controlled for potential confounding factors such as latitude and year of collection.
They then compared the rate of morphological change with each species’ body size, finding that smaller birds tended to undergo more rapid changes in their morphology than larger birds. The researchers attributed this to smaller birds’ higher metabolic rates and faster life cycles, which allow them to adapt more quickly to environmental changes.
“The relationships between body size and rates of change are remarkably consistent across both datasets. However, the biological mechanism underlying the observed link between body size and rates of morphological change requires further investigation,” said U-M ornithologist Benjamin Winger, one of the study’s two senior authors, an assistant professor of ecology and evolutionary biology, and an assistant curator at the Museum of Zoology.
In a study published in the Proceedings of the National Academy of Sciences, researchers analyzed data from 129 bird species, 52 of which were migratory species breeding in North America and 77 were South American resident species. The study investigated whether two fundamental organismal traits, body size, and generation length, shaped the birds’ responses to rapid environmental change. The researchers found that a species’ mean body size was significantly associated with the rates of change measured in both the Chicago and Amazonian birds.
However, available data did not allow the researchers to test whether the observed size shifts represent rapid evolutionary changes in response to natural selection. The study suggests that large body size could further exacerbate extinction risk by limiting the potential to adapt to rapid, ongoing anthropogenic change. On the other hand, smaller-bodied birds might evolve faster because they experience stronger selection, are more responsive to selection, or both.
In conclusion, the study found that bird species with smaller body sizes are shifting faster in response to rapid environmental changes, such as global warming. Body size appears to be a primary mediator of birds’ responses to contemporary climate change. The findings suggest that larger-bodied birds could be at a higher risk of extinction due to their slower response to environmental changes. The study highlights the importance of considering organismal traits, such as body size, in predicting a species’ ability to adapt to rapid environmental changes. However, further research is needed to determine if the observed size shifts represent rapid evolutionary changes in response to natural selection.
- Marketa Zimova, Brian C. Weeks, David E. Willard, Sean T. Giery, Vitek Jirinec, Ryan C. Burner, and Benjamin M. Winger (2023). Body size predicts the rate of contemporary morphological change in birds. Proceedings of the National Academy of Sciences, 120(20), e2206971120. DOI: 10.1073/pnas.2206971120