According to a new report by the nonprofit National Audubon Society, nearly 60% of the 305 species of birds found in North America are on the move—shifting their ranges northward by an average of 35 miles—as a result of global warming. Audubon scientists analyzed 40 years of data from its annual nationwide Christmas Bird Counts to come up with the startling evidence of global warming's impact on natural systems.
While population shifts among individual bird species may be common, Audubon scientists say the ongoing trend of movement by some 177 species in recent years reveals an undeniable link to climate change.
"Birds are showing us how the heavy hand of humanity is tipping the balance of nature and causing ecological disruption in ways we are just beginning to predict and comprehend," said Audubon's Greg Butcher, co-author of the new study. "Common sense dictates that we act now to curb the causes and impacts of global warming to the extent we can, and shape our policies to better cope with the disruptions we cannot avoid."