干旱区生态环境知识资源中心

We developed and tested a 10-min call-broadcast survey protocol using conspecific vocalizations to assess Peregrine Falcon (Falco peregrinus) territory occupancy in the Mojave Desert of southern Nevada and northwestern Arizona from 2008-10. Response rate of peregrines, when adults were confirmed present immediately prior to broadcasting, averaged 83% during the breeding season and peaked at 100% during the courtship stage. Detection trials conducted at known occupied territories, when peregrine locations were unknown at the time of the broadcast, resulted in an average 78% detection rate across the breeding season, as compared to a 79% detection rate using the 4-hr default passive survey protocol from 2006-09. We detected peregrines in 42% of broadcast trials during the post-breeding period (September October) in 2009. We did not observe differences in response rates related to time of clay or distance from the broadcast point to the eyrie (85-1600 m). All peregrine responses during detection trials occurred within 300 sec after beginning the call-broadcast, and the mean duration of response by breeding stage diminished as the breeding season progressed. Response rates were similar by sex (male = 60%, female = 66%), but males were more likely to respond with females than alone. Peregrines often responded in the vicinity of eyries (72% of responses), a behavior we found useful for identifying eyrie ledges early in the breeding season. We found that conducting 10-min call-broadcast, trials early in the peregrine breeding season at distances <= 700 m from the eyrie provided an effective means to assess occupancy.