Post-fledging survival and dispersal of Peregrine Falcons during a restoration project

Abstract

We monitored 38 juvenile Peregrine Falcons (Falcon peregrinus) up to 3 mo immediately after their release from a hack box during 1999-2000. The restoration site was a cliff near Eagle Point Park in Dubuque, Iowa. Falcons were released in a staggered manner from mid-June until late July each summer. Older falcons remained at the site longer than at previous urban releases and interacted with the younger falcons. The four mortalities (11%) confirmed during the observation periods were discovered and reported by citizens near the release site. We used radiotelemetry, observations of color-marked birds at the hack site, and recovered mortalities to estimate weekly survival rates and dispersal patterns. We estimated weekly survival rate to be 0.988 (SE = 0.01), and our weekly resighting rate was high: 0.885 (SE = 0.03). Juveniles were observed for an average of 4.3 wk in 1999 (SD = 2.5), but only 3.4 wk in 2000 (SD = 2.3). Accordingly, weekly fidelity rates were year-specific: 0.903 (SE = 0.03) in 1999 and 0.795 (SE = 0.05) in 2000. No mortalities were attributed to Great-horned Owl (Bubo virginianus) predation, but substantial numbers of owls were seen in summer 2000. The presence of owls in 2000 may have contributed to the difference in fidelity rates and dispersal patterns between years. © 2002 The Raptor Research Foundation, Inc.