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Wednesday, March 19, 2014

Chickadee study shows climate change affecting bird distribution

Carolina Chickadee (left) by Diane Lepkowski/Cornell Lab; Black-capped Chickadee (right) by Ann Marie Halstead/Cornell Lab.

Warming Temperatures Are Pushing Two Chickadee Species Northward
map of chickadee hybrid zone

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


WisconsinWildMan said...

This is pretty interesting. We aren't seeing the Carolina Chickadee in WI to the best of my knowledge, but I have some friends who have indicated that they've seen rises in Northern Cardinals and Brown Headed Cowbirds and felt that this may be due to warmer temperatures. I wonder if anyone is looking at other species.

Wild Birds Unlimited Mid-Michigan said...

That's a very good observation. Certain birds do really well near human dwellings. House Finches, House Sparrows, starlings and cardinals to name a few. Cardinals have been traditionally more common in warmer climes such as the southeastern U.S. However, in recent decades, as you've noticed, they too have expanded their common range north and west in North America. Speculation is that the population growth could be related to an increase in winter birdfeeding but probably more due to the bird's compatibility to human habitats.

Cardinals and Cowbirds are both edge-of-the-woods nesters and most older suburbs provide the perfect breeding territory.

Thank you for commenting! Sarah