ESTABLISHMENT AND GROWTH OF THE PEREGRINE FALCON BREEDING POPULATION WITHIN THE MID-ATLANTIC COASTAL PLAIN

Between 1975 and 1985, 307 captive-reared Peregrine Falcons (Falco peregrinus) of mixed heritage were released within the mid-Atlantic Coastal Plain, a physiographic region with no historical breeding population, as part of the eastern peregrine recovery program. We have monitored the size, distribution, reproductive rate, and substrate use of the resulting breeding population (1979-2007). The population proceeded through an establishment phase (1979-1985) driven by releases with an average population doubling time of 1.3 yr to a consolidation phase (1986-2007) with an average doubling time of 23.4 yr. The region supported 55 breeding pairs by 2007. Reproductive rates have increased significantly over the study period from 1.18 young/occupied territory (1980-1987) to 1.87 young/occupied territory (1998-2007), and average nesting success increased from 66.3% to 79.9%. All breeding pairs nested on artificial substrates, including towers built for the peregrines (n = 37), bridges (n = 29), buildings (n = 7) and an assortment of other structures. Substrate use has diversified over time, with towers making up 100% of nesting structures in the early period of establishment and only 45% by 2007. The population appears to be self-sustaining, with reproductive rates exceeding 1.5 young/occupied territory every year since 1999.