Hacking is placing young birds in a rooftop or elevated enclosure for several weeks until they're ready to fledge, or fly from the nest. At that time the enclosure is opened, and the birds come and go as they please. Eventually they leave, but some will return to hacking areas to nest in subsequent years. Pennsylvania's nesting population numbers about a dozen pairs. All recent nests have been on buildings and bridges in urban settings.
Peregrines remain an endangered species in the commonwealth.
Nationally, however, peregrines were recently removed from the federal Endangered Species List. National delisting was a direct result of the bird's dramatic recovery across the country. Underparts are whitish to buffy colored, broken by horizontal bars. Birds up to two years old are marked with dark brown, rather than gray, on their wings and back. Like all falcons, the peregrine has long pointed wings and rapid, steady wing beats in flight.