As part of the Natural Resource Challenge (NPS 1999), the Mid-Atlantic Network (MIDN) has been tasked with monitoring "vital signs," a suit of physical, chemical, or biological elements or processes that represent the overall health or condition of the network parks' natural resources. Breeding birds have been selected as one of the Mid-Atlantic Network's vital signs because they are highly visible, are a reliable indicator of ecological integrity, and face numerous population threats in the region (Comiskey and Callahan 2008).