One bird that almost all easterners recognize and enjoy is the Chickadee. What some people in our locale do not know is that it is possible to have two Chickadee species stopping by our feeders in winter. People frequently assume that the Chickadees observed around SE Pennsylvania are Black-capped. In truth most of our local chickadees are Carolina. Black-cappeds come south in what is called irruptive years. Irruptive years occur when a lack of food forces Black-cappeds south.
How do you tell the Black-capped from the Carolina? First clue is geography. The soft dividing line between Black-capped and Carolina runs from Palm, PA in northern Montgomery County through Doylestown, PA. Any bird in the Appalachian mountain zone is most likely a Black-cappped. Birds within 12 miles north or south of the intersection line are possible hybrid between the two.
A second clue is song. Black-cappeds tend to have a slower, deeper chickadee song. The fee-beeyee call is also slower. Carolinas tend to have rapid and incessant chickadee song. The call is more fee-bee-fee-bay.
A third clue is size. Black-capped Chickadees always look to me like a Chickadee on steroids. Their head and necks look huge. Their tails are longer. To me the Carolina looks dainty and small headed.
A fourth clue is markings. Black-capped Chickadees have a white hockey stick that seems to border the outer primary feathers (flight feathers) that run into the primary coverts (the feathers that cover the start of the primary feathers). The outer tail feathers many also show a white tone. Black-cappeds in general are much more contrasting, especially from the back. I have a tendency to look for contrast between the white at the cheek (auricles) and the black crown and nape (back of neck). Black-cappeds usually show a sharp demarcation between the black nape, white cheek, and brownish or olive-gray mantle. Carolinas have less white along primary feathers, show a gray mantle that seems to seep into the white cheek (auricles). You can also look to see if the black bib is clean (Carolina) or messy (Black-capped).
So when I am walking into the woods trying to figure out what Chickadee I have, I think: What time of year is it? (Most Spring, Summer, and Fall birds are most likely Carolina); Where am I at? (Geography); What song do I hear? (fast or slow). When I see the bird, I look for the size; how much contrasting I see from the side and the back; and does it have a white hockey stick at the flight feathers. So the next time you are in the woods or checking birds at your feeder see if you can see the difference between these two delightful little species.
In the pictures below see if you can see the differences.