Who’s That At My Feeder?
(This Friday, we’re taking a break from T.G.I.F. with Tom Barnes to hear from bird lover Deb Reynolds with the U.S. Fish and Wildlife Service’s Division of Migratory Birds)
“Chicka dee dee dee.” The familiar sound of the chickadee is easy to recognize. As a Massachusetts native, I grew up with chickadees at my backyard feeder. With its black cap, white cheek patches and year-round residency, who could mistake it for anything but a black-capped chickadee? Turns out, the effects of a changing climate may be fooling many of us!
Another species, the Carolina chickadee, lives in the southern portion of the United States. There is a small band of land, 21 miles on average where Carolina and black-capped Chickadees overlap and breed. This is called the hybrid zone. When the two species breed, their chicks do not have the same rate of survival as when the parents of the same species breed. This low survival rate keeps the hybrid zone narrow and well defined.
This hybrid zone was the backdrop of a study that began nearly 20 years ago by Villanova University biology professor Robert Curry. Dr. Curry wanted and easy-local project where he and his students could keep track of a lot of birds. He chose to study these two chickadee species with the ultimate goal of pinning down the boundary of the hybrid zone. He and his students set up 450 fake nests, banded the birds and kept track of everything they did, from who they bred with, how many chicks they had, and where the survivors went.
As his study stretched on, something unexpected happened. The hybrid zone – that ribbon of land that separates the northern and southern chickadee species – was moving north due to climate change.
Carolina chickadees, like lots of people who live in the South, don’t like the cold. As winter temperatures rise, they expand their range, pushing that hybrid zone north. Dr. Curry found that Carolina chickadees were moving north at the same rate as warming temperatures were being observed. He said he was struck by “how strong the climate signal was” and didn’t think he and his students would be able to show it as quickly and clearly as they did.
This clear documentation of rising temperatures affecting one of our most common and beloved species has implications for people, too. The northward movement of birds means other things are moving as well, like parasites to disease and insects that could affect agriculture.
When the Massachusetts state bird, the black-capped chickadee, gets pushed so far north that we no longer see the beloved and familiar friend at our feeder, we know the world is changing – even in our own backyards.
For more details about Dr. Curry’s study, visit: http://articles.philly.com/2014-03-19/news/48334893_1_chickadees-hybrids-hawk-mountain-sanctuary.
Read the latest publication on this research in Current Biology