Our Response - Page 7
Peregrine Falcons introduced into the Commonwealth of Pennsylvania have established self-sustaining populations which continue to grow above earlier forecasts by USFWS and above the minimum number of successful nesting pairs originally proposed by PGC biologists. USFWS delisted the Peregrine in 1999 based on the then existence of more than 40 breeding pairs producing 1.92 young/pair compared to a recovery goal of 22 pairs producing 1.5 young/pair for the Commonwealth of Pennsylvania.
The PGC set a recovery goal based on 50% of the highest historic number of nesting peregrines reported in Pennsylvania of 44 pairs. That recovery goal was reached in 2008 with at least 23 known nesting pairs in PA.
3 Beebe attributed the difference in size to its primary prey base which would have been the passenger pigeon – a colonial breeding bird of the region. He hypothesized that the size of raptors is determined by the size of the primary prey base during the breeding season and the tiercel’s (male falcon) ability to catch it in sufficient numbers and carry it back to the eyrie efficiently. If tiercels are unable to do this, there can be no breeding success. The tiercel Eastern anatum was the perfect size to catch and carry passenger pigeons. The Western anatum did not have this evolutionary pressure for similar sized prey. (Frank Beebe, Personal communication, 2005)
and produced 60 fledglings. By 2012, PA is known to have a minimum of 32 active nests producing ever growing numbers of fledglings.