In Pennsylvania, Black-capped Chickadees and Carolina Chickadees come into parapatric contact along a long, narrow zone. In this zone, the species hybridize, and the presence of each influences the social development of the other.
This project involves intensive field study of four populations:
- Great Marsh (Chester Co.): Carolina Chickadees
- Nolde Forest Environmental Education Center (Berks Co.): formerly hybrid chickadees; now all Carolina Chickadees
- Hawk Mountain Sanctuary (Berks & Schuylkill Cos.): formerly all Black-capped Chickadees; now, mixed population
- Tuscarora State Park (Schuylkill Co.): Black-capped Chickadees
At all study sites, we use artificial nest snags to attract breeding chickadees and to obtain data about their behavior, genetics, and success … and to band and obtain genetic samples from their nestlings.
The study now focuses especially on rapid northward movement of the hybrid zone. Our collaborative work with the Lovette Lab at Cornell has identified a strong signal linking the hybrid-zone movement with climate change … including in particular warming winter low temperatures.