Peregrine falcons at two Pennsylvania nests monitored by livestreaming cameras are tending to eggs laid in those nests recently.
The peregrines at the nest on the Rachel Carson State Office Building in Harrisburg are incubating five eggs that the female laid from March 7-16.
The female had laid two eggs as of today in the nest at the University of Pittsburgh’s Cathedral of Learning in Pittsburgh.
Female peregrines typically lay three to five eggs, which the pair of falcons then incubate for about 33-35 days.
Activities at both nests is available for online viewing through 24-hour livestreaming cameras. The Harrisburg nest can be viewed through the Pennsylvania Falcon Cam webpages. The Pittsburgh nest can be seen through the National Aviary’s livestreams webpage.
After hatching, peregrine chicks spend about six weeks in the nest before they are ready to fledge. After that, the young falcons will spend the summer with their parents before moving on to stake out their own territories.
The Harrisburg nest fledged two chicks last year, while the Pittsburgh nest fledged four in 2021.
Peregrine falcons are well known for nesting on man-made structures, including buildings and bridges, but their historical nesting aeries were on rock ledges and natural cliff sites.
The Rachel Carson building has been home to a pair of peregrines since 1997, while the Cathedral of Learning has seen a pair of nesting peregrines since 2001.
The species was listed as endangered in Pennsylvania until 2019, after the populations plummeted in the mid-20th century due to the widespread use of the pesticide DDT. The conservation status was recently upgraded to threatened in Pa., after a steadily growing population led to pairs re-occupying several historically occupied natural cliff-nesting sites in the northeastern part of the state.
It was removed from the federal Endangered Species List in 1999.
According to the Pennsylvania Game Commission, peregrines historically nested widely in the eastern U.S., numbering about 350 nesting pairs in the early 1900s. In Pennsylvania, there were 44 known nest sites. Most were on cliffs, usually along rivers.
The native eastern breeding population was wiped out by the early 1960s, primarily due to effects of DDT. No nesting records were known in Pennsylvania between about 1959 and 1987.
Cliff-nesting – where most peregrines nested in Pennsylvania prior to their population collapse and eventual extirpation – was first reconfirmed in the state in 2003 at a site in Lycoming County. The statewide population experienced a surge from 13 pairs in 2006 to 23 pairs in 2007.
The number of nesting pairs in the state surpassed 30 in 2011, with most nests on manmade structures. In 2013 there were 40 known nests, closing in on Pennsylvania’s pre-DDT total of 44. That number has now been surpassed.
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