We monitored 256 Peregrine Falcon (Falco perigrinus) nest-sites, accumulating 852 site-years in Colorado, Wyoming, and Montana during 2005–2009. The sites included 42 selected by the U.S. Fish and Wildlife Service for its monitoring program in 2006 and 2009. Annual nest occupancy rates ranged from 75 to 100% and varied as much as 10% among years in each state, and 25% among states. Nest success was 77% overall (n = 687), but differed as much as 25% among states in 2009. Reproduction rate was 1.8 young/pair for 687 nesting attempts where outcome was known, and annual state averages ranged from 1.2 to 2.2 young/pair. We discovered or were alerted to 77 pairs at new locations, suggesting that future searches will be successful. Overall, 353 nesting locations in the three states combined had been recorded at the end of the 2009. Wide variations among years in occupancy, nest success, and reproduction underscore the necessity of long-term monitoring of Peregrine Falcons on a regional, rather than a state, perspective.
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