Climate Change Impacts Cast of Winter Birds in North America

Climate change may be impacting what birds show up where during the winter. Scientists have found that the resident communities of birds that appear at eastern North America's backyard bird feeders in winter have changed as temperatures have warmed.

In order to better understand how the cast of birds has changed, the researchers used more than two decades of data on 38 species gathered by thousands of citizen scientists. This revealed that birds that are typically found in more southerly regions have steadily pushed northward.

"Fifty years ago, cardinals were rare in the northeastern United States," said Benjamin Zuckerberg, one of the researchers, in a news release. "Carolina wrens even more so."

The scientists measured the changes over time in the abundance of 38 bird species at feeders in eastern North America. More specifically, they examined the influence of changes in winter minimum temperature over a 22-year period on the flocks of birds that gather at backyard feeding stations.

"We've been able to document in past studies that species are shifting in response to climate change," said Zuckerberg. "This study documents changes in the (winter bird) community structure. If you have a species coming into a new area, it can modify the composition of the community. These backyard birds are the canaries in the coal mine. Birds have always been very good indicators of environmental change. Whenever you have a reshuffling of a community of species, you have less of a sense of what change is going to be."

The findings reveal that species are indeed shifting. With milder winters and less snow, it's likely that these changes will continue. This, in turn, could impact ecosystems all along wintering grounds in North America.

The findings are published in the journal Global Change Biology.