ZooAmerica Conservation News: April 2022

ZooAmerica’s Role in the Pennsylvania Peregrine Recovery

Peregrine Falcons have never been common in Pennsylvania. There were 44 known peregrine nests in the state before their extirpation from the eastern United States in the early 1960s due to the effects of the pesticide DDT. 

No peregrines nested in Pennsylvania for nearly thirty years, from 1959 to 1987. After DDT was banned in the 1970s, The Peregrine Fund initiated some reintroduction releases into the eastern U.S. This was the beginning of a slow but steady expansion. By the late 1980s, several pairs of peregrines were nesting on man-made structures in Pennsylvania, such as bridges spanning the Delaware River in the Philadelphia area. In the 1990s, the Pennsylvania Game Commission began a reintroduction effort, spearheaded by PGC Biologist Dan Brauning, to augment the natural expansion that was slowly occurring. 

ZooAmerica became a partner in the project, along with local falconer Alan Pollard, to produce young falcons for the release effort. Nestlings hatched under the bridges over the Delaware rarely survived, as their first flight usually ended in the river. We would collect eggs from the bridge nests, hatch them under Alan’s falcons, and then release them at “hacking’ sites around the state. The bridge pairs would lay a second clutch of eggs about two weeks after we collected the first clutch. We also produced chicks for the release project at ZooAmerica, where we had four pairs of peregrines laying eggs. 

In the pre-DDT era, nearly all peregrines nested on cliff ledges. But the newly established population showed a strong preference for man-made structures, nesting under bridges and on the sides of tall buildings. Chick survival on man-made structures is much lower than at cliff sites, as the fledglings get hit by cars or drown in the rivers. 

Our state’s first confirmed cliff-nesting pair of the post-DDT era was at a location along the Susquehanna in Lycoming County in 2003. The male of this pair was a bird produced at ZooAmerica and released from a hack site on the roof of the Genetti Hotel, Williamsport’s tallest building. “Zoo #1”, as this male was named, fathered offspring at the cliff site for some years to come. As of 2021, there were 73 nesting pairs of peregrines in Pennsylvania. Peregrines can often be seen perched on the old cocoa bean silos adjacent to the zoo and may have attempted to nest there last year. It is deeply satisfying to have played a part in this successful reintroduction effort.