ITHACA, N.Y. – The zone of overlap between Caroline chickadees and black-capped chickadees, two closely related backyard birds, is moving northward at a rate that matches warming winter temperatures, according to a study by researchers from the Cornell Lab of Ornithology and Villanova University.
In a narrow strip that runs across the eastern U.S., Carolina chickadees from the south meet and interbreed with black-capped chickadees from the north. The new study finds that this hybrid zone has moved northward at a rate of 0.7 mile per year over the last decade. The research was published online in Current Biology on March 6, 2014.
“A lot of the time climate change doesn’t really seem tangible,” said lead author Scott Taylor, a postdoctoral researcher at the Cornell Lab of Ornithology. “But here are these common little backyard birds we all grew up with, and we’re seeing them moving northward on relatively short time scales.”
Chickadees — there are seven species in North America — are fixtures in most of the backyards of the continent. These tiny, fluffy birds with bold black-and-white faces are favorite year-round visitors to bird feeders, somehow surviving cold winters despite weighing less than half an ounce.
To the untrained eye the Carolina Chickadee of the southeastern U.S. is almost identical to the more northern Black-capped Chickadee — although the Carolina has a shorter tail, less white on its shoulders, and a song of four notes instead of two notes. Genetic research indicates the two have been distinct species for at least 2.5 million years.
“The rapidity with which these changes are happening is a big deal,” Taylor said. “If we can see it happening with chickadees, which are pretty mobile, we should think more closely about what’s happening to other species. Small mammals, insects, and definitely plants are probably feeling these same pressures — they’re just not as able to move in response.”