Warming Temperatures Are Pushing Two Chickadee Species Northward
The two chickadee species meet and hybridize in a narrow zone
that has shifted northward 7 miles in the last decade.
News release: Ithaca, N.Y.—The zone of overlap between two popular, closely related chickadee species is moving northward at a rate that matches warming winter temperatures, according to a study published online in Current Biology.
In a narrow 21 miles across strip that runs along 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.
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.
“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.”
“Hybridization is kind of a brick wall between these two species,” said Robert Curry, a professor of biology at Villanova University, who led the field component of the study. “Carolina Chickadees can’t blithely disperse north without running into black-caps and creating hybrids. That makes it possible to keep an eye on the hybrid zone and see exactly how the ranges are shifting.”
Female Carolina Chickadees seem to be leading the charge, Curry said. Field observations show that females move on average about 0.6 mile between where they’re born and where they settle down. The warmer the winters the further north they can settle.
“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.”
Read the full report at: http://www.sciencedirect.com/science/article/pii/S0960982214001341
Watch the video at: http://youtu.be/n81Pwweb62Y