Turnover and dispersal of Prairie Falcons in southwestern Idaho

We studied Prairie Falcon (Falco mexicanus) breeding dispersal, natal dispe rsal, and turnover at nesting areas inn the Snake River Birds of Prey Natio nal Conservation Area (NCA) from 1971-95. Of 61 nesting areas where falcons identified one year were known to be present or absent the following year, 57% had a different falcon. This turnover rate was 2-3 times higher than t hat reported elsewhere for large falcons, and may have been related to high nesting densities in the NCA. Turnover at nesting areas was independent of nesting success in the previous year, but was significantly higher for fem ales nesting on large cliffs. Mean distance between natal and breeding loca tions for 26 falcons banded as nestlings and later encountered as nesting a dults was 8.9 km. Natal dispersal distances were similar for males and fema les, but more than twice as many males marked as nestlings were later encou ntered nesting in the NCA. Fourteen adult falcons found on different nestin g areas in successive years moved an average of 1.5 km between nesting area s; males dispersed significantly farther than females. Natal and breeding d ispersal distances in the NCA were lower than those reported for Prairie Fa lcons in other study areas. Only four falcons banded as nestlings were foun d outside NCA boundaries during the breeding period, and only one of these birds was known to be occupying a nesting area. We encountered no falcons b anded outside the NCA occupying nesting areas in the NCA during this study.