If you want to spot a “cute” backyard bird, look no further than the chickadee. Black-capped chickadees and Carolina chickadees have wide ranges in the United States and both have very similar features – black caps, black bibs, gray wings and back, and a whitish underside. How do you tell them apart? Black-capped Chickadees have larger white patches on their wings while Carolina Chickadees have mostly gray wings. They also have different ranges: Black-capped chickadees are found in the northern part of the country and Carolina chickadees are found in the souther part of the country. A hybrid zone running mostly east-west from New Jersey through Pennsylvania and over across the midwestern states is an area where these two ranges overlap and interbreeding between the two species occurs. The location of the hybrid zone is also a good indicator of environmental change.
So what’s the deal with the hybrid zone? The ranges of these chickadees have moved northward at 0.7 miles per year over the last decade. Genetic data and eBird sightings taken from 2000-2002 and 2010-2012 were examined to map the hybrid zone, showing a shift northward. Hybrids usually occur in areas where average low winter temperatures are about 14-20 degrees Fahrenheit. Temperature records show that this temperature range also shifted north over the study period, corresponding with the hybrid zone shift of seven miles north since 2000. One of the study sites that started out in the middle of the hybrid zone was home to almost purely Carolina Chickadees by the end of the study period.
Are you noticing Black-capped Chickadees or Carolina Chickadees in your area? Take a photo and upload it to the Eyes on Central PA Mission on Project Noah. Your photo may be featured on this blog or in Chief Meteorologist Joe Murgo’s next on-air broadcast!