Warming World Reshapes Cast of Winter Birds in Northeast

Our warming world 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 increased.

For the average bird watcher, seeing cardinals, chipping sparrows or Carolina wrens frequenting their backyard birdfeeders is nothing out of the ordinary. But in this warming world, these and other warm-adapted species have greatly expanded their wintering range, a change that may have unforeseen consequences for North American ecosystems, according to University of Wisconsin-Madison wildlife biologists Benjamin Zuckerberg and Karine Princé.

In a new paper published in the journal Global Change Biology, Zuckerberg and Princé analyzed more than two decades of data on 38 species of birds gathered by thousands of citizen scientists.

"Fifty years ago, cardinals were rare in the northeastern United States," Zuckerberg explained in a press 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," Zuckerberg said. "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," he added. "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."

And with climate models predicting temperatures to warm even more over the next century, milder winters with less snow could become the norm, making it so we don't even recognize the bird species in our backyards anymore.