Peregrine falcons (Falco peregrinus) have nested on bridges in Portland, Oregon since at least 1994. In 2002, the Oregon Department of Transportation (ODOT) worked with the Audubon Society, and state and federal regulatory agencies to develop a peregrine falcon management plan. A primary goal of the plan was to enable ODOT to address the challenges posed by operating and maintaining major transportation infrastructure that also serves as nesting habitat for peregrine falcons. Mason, Bruce & Girard, Inc. (MB&G) has been involved in the monitoring effort since development and implementation of ODOT’s peregrine falcon management plan. We describe the survey protocol followed over the years to determine nest site occupancy status, chronology, and success, as well as peregrine behavior during disturbances associated with ODOT maintenance actions near the nest locations. We also discuss the unique opportunities, threats, and challenges faced by peregrine falcons that select nest sites on urban structures.
Results/Conclusions
We report the results of combined Audubon Society and MB&G survey data on site occupancy, nest success, and productivity for 11 ODOT bridges in the Portland metro area. Surveys were completed at individual bridges for up to 23 years. Between 1994 and 2019 the occupancy rate of surveyed bridges was 89% and resulted in the confirmed production of 133 eyases. Between 1994 and 2010, when bridges were more consistently surveyed long enough through the nesting period to determine success, the productivity rate of Portland area bridges ranged between 0 and 2.9 eyases per nesting season per bridge with an average of 1.89 eyases per nesting season per bridge. These urban structures therefore contributed long-term successful nesting locations for peregrine falcons during their recovery. Primary ongoing challenges include contaminants, disturbance from urban-area activities; post-fledging: vehicle collision, drowning, window strike, poisoning, dog or cat attack, raccoon predation. Conflicts have been reduced by careful timing of bridge maintenance and construction activities to reduce disturbance. In cases where nest abandonment appears likely, young are removed from the nest and raised in Audubon’s captive rearing program.