Effects of forest fragmentation on chickadee reproduction in southeastern Pennsylvania

Negative impacts of forest fragmentation on migrant songbirds, habitat specialists requiring large forests to breed successfully, have been well documented. Little was known about these impacts on resident, cavity-nesting birds, species considered less affected by fragmentation. I compared reproductive variables of Black-capped Chickadees (Poecile atricapillus) inhabiting woodlots of varying sizes at Hawk Mountain Sanctuary. I tested for presence of edge effects, particularly nest usurpation by House Wrens. The discovery of Carolina Chickadee (Poecile carolinensis) haplotypes within this population added a confounding variable; however, parental haplotype did not influence nest success. Woodlot size did not influence chickadee nest success (n = 48). Chickadees chose edge over forest interior when nesting, despite increased presence of House Wrens. Earlier laying dates in smaller, edge-dominant woodlots suggest chickadees were responding to local edge effects. This was the first study to document the effects of forest fragmentation on a hybridizing chickadee population in southeastern Pennsylvania.