Similar response to climate change in European and US birds

Common birds in the United States and Europe have responded in similar ways to climate change in the last 30 years.

“There are a lot of things that drive populations of animals to go up and down in number,” said Philip Stephens, an ecology professor at Durham University in England and lead author of a recent study published in the journal Science. “It’s difficult to tease out the effects of one particular driver.”

In an effort to do so, Stephens and other collaborators from across Europe and the U.S. conducted a study to look at the fates of common bird species that could be affected by climate change. After reviewing the average climates in areas where each species was found, the team split the birds into two categories: species in which climate change seemed to be leading to more favorable climates and those where climate change was apparently leading to deteriorating climates.

Abundance data including 145 common bird species in Europe and 380 common bird species in the U.S. collected by thousands of volunteers from 1980 to 2010 showed that on both continents the birds expected to do better as a result of climate change had, in fact, substantially outperformed those expected to suffer from climate change. This is a clear demonstration of the role that climate change has played in affecting the abundances of hundreds of species, Stephens said.

For example, the Anhinga (Anhinga anhinga) and Cassin’s kingbird (Tyrannus vociferans), which were both once strongholds in the south, according to Stephens, are now increasingly common farther north. In Europe, species such as the wren (Troglodytidae) have been increasing in northern areas where winters are becoming milder and declining in southern countries with hotter and drier summers.

The team also took note of other factors that might lead to biases including species’ body size, migratory behavior and habitat affinities, but their analysis found these didn’t differ systematically between the groups that were either advantaged or disadvantaged by climate change.

Stephens said the data collected by volunteers with USGS and the Pan-European Common Bird Monitoring Scheme can be used to see how birds will be affected by climate change in the future. Meanwhile, he hopes lobbyists use this study to illustrate the scale of changes due to climate change.

“As an ecologist, impacts of climate change for the future often look bleak,” he said. “We’re looking at what’s already happened. This is a striking illustration that I hope will be clear to policy makers.”

Further, the study is important because sometimes species change in abundance with no real explanation. This research can show whether climate change is behind some of these changes.


Header Image: The American robin, which is common across the continental U.S., has declined in southern states such as Mississippi and Louisiana but increased in north-central states including North and South Dakota.
©David A Mitchell